<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:06481628-a5c2-4627-98e6-912ddf89737f,g:f2f9f021-b4d4-406f-b721-7101de0c2efa-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://acmrcsh.com/role/CoverPage" xlink:type="simple" xlink:href="acmr-20250930.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_3ef8ac9f-5daa-4af5-b174-fdb8f4d8f248" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_DocumentInformationTable_3ef8ac9f-5daa-4af5-b174-fdb8f4d8f248" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_a7c0f0ec-a628-4e02-8ccd-00cfbbbefd07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_3ef8ac9f-5daa-4af5-b174-fdb8f4d8f248" xlink:to="loc_us-gaap_StatementClassOfStockAxis_a7c0f0ec-a628-4e02-8ccd-00cfbbbefd07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a7c0f0ec-a628-4e02-8ccd-00cfbbbefd07_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_a7c0f0ec-a628-4e02-8ccd-00cfbbbefd07" xlink:to="loc_us-gaap_ClassOfStockDomain_a7c0f0ec-a628-4e02-8ccd-00cfbbbefd07_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d452f108-57e0-4d8a-99d0-25ed4b1bcfec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_a7c0f0ec-a628-4e02-8ccd-00cfbbbefd07" xlink:to="loc_us-gaap_ClassOfStockDomain_d452f108-57e0-4d8a-99d0-25ed4b1bcfec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_a9c9a31f-470d-425c-8ed9-812bf70c91a7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_d452f108-57e0-4d8a-99d0-25ed4b1bcfec" xlink:to="loc_us-gaap_CommonClassAMember_a9c9a31f-470d-425c-8ed9-812bf70c91a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_c1cabc18-89d5-46f7-ab64-27ddc279e995" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_d452f108-57e0-4d8a-99d0-25ed4b1bcfec" xlink:to="loc_us-gaap_CommonClassBMember_c1cabc18-89d5-46f7-ab64-27ddc279e995" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_707258e3-df71-4ae7-8cbc-139be041f1a9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_DocumentType_707258e3-df71-4ae7-8cbc-139be041f1a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_b68fd793-ed3e-4569-a64b-0772f8fa3107" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_DocumentQuarterlyReport_b68fd793-ed3e-4569-a64b-0772f8fa3107" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_ef4752c5-d784-4b08-87f6-1ad4f6886dc6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_DocumentPeriodEndDate_ef4752c5-d784-4b08-87f6-1ad4f6886dc6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_f79a768e-08f5-4a1c-bde4-b14dd5aafec1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_DocumentTransitionReport_f79a768e-08f5-4a1c-bde4-b14dd5aafec1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_ee4313ad-880b-43f8-8069-f21a5558c21c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityFileNumber_ee4313ad-880b-43f8-8069-f21a5558c21c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_b23f5e95-8a92-48a6-97b7-949f342bf6e1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityRegistrantName_b23f5e95-8a92-48a6-97b7-949f342bf6e1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_8beebe71-d56f-404d-b40f-d5918f008273" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityIncorporationStateCountryCode_8beebe71-d56f-404d-b40f-d5918f008273" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_861ef8ff-7053-4025-8344-b3b43c681dce" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityTaxIdentificationNumber_861ef8ff-7053-4025-8344-b3b43c681dce" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_6b67c395-ac20-45cc-8d42-d4c239f38c18" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityAddressAddressLine1_6b67c395-ac20-45cc-8d42-d4c239f38c18" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_7855d0ed-a131-4175-bc20-797f730c00f6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityAddressCityOrTown_7855d0ed-a131-4175-bc20-797f730c00f6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_982bba9a-ce7b-480d-a6fc-adb2a5e42e0a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityAddressStateOrProvince_982bba9a-ce7b-480d-a6fc-adb2a5e42e0a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_745cb783-6201-4a54-b007-fc04b32193e4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityAddressPostalZipCode_745cb783-6201-4a54-b007-fc04b32193e4" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_74352e17-93ef-47df-8dea-e02d9600805d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_CityAreaCode_74352e17-93ef-47df-8dea-e02d9600805d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_67c38efb-1409-48f5-b4e5-608934fc0d56" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_LocalPhoneNumber_67c38efb-1409-48f5-b4e5-608934fc0d56" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_e555f12e-e89f-4fdd-9e2a-59d677e43197" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_Security12bTitle_e555f12e-e89f-4fdd-9e2a-59d677e43197" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_7ae8f1cf-c6ae-4d80-805c-522e443cc8f9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_TradingSymbol_7ae8f1cf-c6ae-4d80-805c-522e443cc8f9" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_c610d9d5-e63b-4d3e-898e-d5d37ded770c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_SecurityExchangeName_c610d9d5-e63b-4d3e-898e-d5d37ded770c" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_f2bf50b2-2c25-44b5-af58-15ba8c43bded" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityCurrentReportingStatus_f2bf50b2-2c25-44b5-af58-15ba8c43bded" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_972fbb27-9145-4924-86a1-38d54240902d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityInteractiveDataCurrent_972fbb27-9145-4924-86a1-38d54240902d" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_d0d36277-b1e3-46fe-8ba2-94417903db96" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityFilerCategory_d0d36277-b1e3-46fe-8ba2-94417903db96" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_3574d419-6f3f-439d-aa02-420c290b2d46" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntitySmallBusiness_3574d419-6f3f-439d-aa02-420c290b2d46" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_213df982-45b9-48b5-87b9-263811ca5f05" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityEmergingGrowthCompany_213df982-45b9-48b5-87b9-263811ca5f05" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_918e919f-cfc3-485a-8349-387752b24ac2" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityShellCompany_918e919f-cfc3-485a-8349-387752b24ac2" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_1796ba04-3bcc-4bde-8e2a-f40f81de8b03" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_1796ba04-3bcc-4bde-8e2a-f40f81de8b03" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_ab418461-164b-42c7-9fd2-c308accfcb4d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_EntityCentralIndexKey_ab418461-164b-42c7-9fd2-c308accfcb4d" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_f6cb8f4f-035f-4fef-9b3c-08f0fb185358" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_DocumentFiscalYearFocus_f6cb8f4f-035f-4fef-9b3c-08f0fb185358" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_78c46ade-514e-4b3b-8537-07bb596c1651" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_AmendmentFlag_78c46ade-514e-4b3b-8537-07bb596c1651" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_df7b0625-da1b-4441-8f2b-f053a105bbc4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_CurrentFiscalYearEndDate_df7b0625-da1b-4441-8f2b-f053a105bbc4" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_e7ed4d0e-12d0-49ec-a1c8-1c5fe18866bf" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_c1b8c74f-0ea3-4bde-bca8-facc6887ea33" xlink:to="loc_dei_DocumentFiscalPeriodFocus_e7ed4d0e-12d0-49ec-a1c8-1c5fe18866bf" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/CondensedConsolidatedBalanceSheets" xlink:type="simple" xlink:href="acmr-20250930.xsd#CondensedConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_b7ff0bd7-8e5c-4546-94a8-370a4a8e2528" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5e6abbc4-a79e-4ac3-b52c-1af1791c0181" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_b7ff0bd7-8e5c-4546-94a8-370a4a8e2528" xlink:to="loc_us-gaap_StatementTable_5e6abbc4-a79e-4ac3-b52c-1af1791c0181" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_df88ad1f-2c37-4a03-afe8-90b8219775d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5e6abbc4-a79e-4ac3-b52c-1af1791c0181" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_df88ad1f-2c37-4a03-afe8-90b8219775d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_df88ad1f-2c37-4a03-afe8-90b8219775d8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_df88ad1f-2c37-4a03-afe8-90b8219775d8" xlink:to="loc_us-gaap_RelatedPartyDomain_df88ad1f-2c37-4a03-afe8-90b8219775d8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_e15b3a98-d7ce-4afb-a1a2-0281080d825e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_df88ad1f-2c37-4a03-afe8-90b8219775d8" xlink:to="loc_us-gaap_RelatedPartyDomain_e15b3a98-d7ce-4afb-a1a2-0281080d825e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_e35cb1a6-d7aa-4dac-bf0f-3c03442afaf5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_e15b3a98-d7ce-4afb-a1a2-0281080d825e" xlink:to="loc_us-gaap_NonrelatedPartyMember_e35cb1a6-d7aa-4dac-bf0f-3c03442afaf5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_091fbfb3-34c9-4c03-90fe-ca92d6480536" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_e15b3a98-d7ce-4afb-a1a2-0281080d825e" xlink:to="loc_us-gaap_RelatedPartyMember_091fbfb3-34c9-4c03-90fe-ca92d6480536" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_68731bb7-09c1-4ff4-8957-bd757c350958" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5e6abbc4-a79e-4ac3-b52c-1af1791c0181" xlink:to="loc_us-gaap_StatementClassOfStockAxis_68731bb7-09c1-4ff4-8957-bd757c350958" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_68731bb7-09c1-4ff4-8957-bd757c350958_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_68731bb7-09c1-4ff4-8957-bd757c350958" xlink:to="loc_us-gaap_ClassOfStockDomain_68731bb7-09c1-4ff4-8957-bd757c350958_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_2947dbfe-3cb4-4227-b13a-69701c7874ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_68731bb7-09c1-4ff4-8957-bd757c350958" xlink:to="loc_us-gaap_ClassOfStockDomain_2947dbfe-3cb4-4227-b13a-69701c7874ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_c0aa5199-b2d1-4d0d-9356-bebb246e9025" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2947dbfe-3cb4-4227-b13a-69701c7874ea" xlink:to="loc_us-gaap_CommonClassAMember_c0aa5199-b2d1-4d0d-9356-bebb246e9025" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_6faac870-d304-48eb-978c-bba86766d77b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2947dbfe-3cb4-4227-b13a-69701c7874ea" xlink:to="loc_us-gaap_CommonClassBMember_6faac870-d304-48eb-978c-bba86766d77b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b7ff0bd7-8e5c-4546-94a8-370a4a8e2528" xlink:to="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_8988dff7-fa1f-4670-8b75-e7828dacc9fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_8988dff7-fa1f-4670-8b75-e7828dacc9fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashCurrent_2f2ae444-46be-471a-b881-06a2d264a7c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedCashCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_RestrictedCashCurrent_2f2ae444-46be-471a-b881-06a2d264a7c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsAssetsCurrent_a037545e-e23e-4fd0-83ea-7e42c6ed84a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepositsAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_DepositsAssetsCurrent_a037545e-e23e-4fd0-83ea-7e42c6ed84a6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_097839cf-390c-4fb4-acf5-e0f4e1b9a04d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_ShortTermInvestments_097839cf-390c-4fb4-acf5-e0f4e1b9a04d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_e9104fd3-548b-4a05-aba2-ade1359e70e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_e9104fd3-548b-4a05-aba2-ade1359e70e1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivablesNetCurrent_07040e92-6b7a-43ef-adc4-0dea481ea499" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_OtherReceivablesNetCurrent_07040e92-6b7a-43ef-adc4-0dea481ea499" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_f42a8555-9d8f-484b-9866-2d5daefb6a01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_InventoryNet_f42a8555-9d8f-484b-9866-2d5daefb6a01" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_3b297852-344c-4969-b1b8-c1a0f7c279c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_3b297852-344c-4969-b1b8-c1a0f7c279c8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_cee41e39-2f66-4eab-a921-0058a49afcfd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_0a43cd89-e0a5-4594-97af-a904f1b4ef8a" xlink:to="loc_us-gaap_AssetsCurrent_cee41e39-2f66-4eab-a921-0058a49afcfd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_3d6ab764-c9d4-4620-b39a-0dcfb97d6fd2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_3d6ab764-c9d4-4620-b39a-0dcfb97d6fd2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_1a4ef921-0091-4591-9f79-9eebcf42bd46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_1a4ef921-0091-4591-9f79-9eebcf42bd46" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_37e65750-f37c-4177-8d99-324696e2c16e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_37e65750-f37c-4177-8d99-324696e2c16e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositsAssetsNoncurrent_12c2f8b1-11cf-4e00-9544-125b455feb10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepositsAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_DepositsAssetsNoncurrent_12c2f8b1-11cf-4e00-9544-125b455feb10" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_ed54f637-c221-4bb7-a58a-191f3295ae09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_ed54f637-c221-4bb7-a58a-191f3295ae09" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermInvestments_a646dc60-11a6-47b4-ba94-74d2041bb294" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_LongTermInvestments_a646dc60-11a6-47b4-ba94-74d2041bb294" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_1c37cb90-42b3-48a2-8b54-72794c223019" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_1c37cb90-42b3-48a2-8b54-72794c223019" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_d81e38f3-6753-45f1-b4f7-cad49761fcf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_4a1469f0-dd57-4fd9-a274-6df2f4a918b2" xlink:to="loc_us-gaap_Assets_d81e38f3-6753-45f1-b4f7-cad49761fcf4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b7ff0bd7-8e5c-4546-94a8-370a4a8e2528" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_e33b1462-bf3b-462c-b255-1ac3a25a3441" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_ShortTermBorrowings_e33b1462-bf3b-462c-b255-1ac3a25a3441" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_a09b0c88-44dd-4f2e-8539-2313c33bd7c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_LongTermDebtCurrent_a09b0c88-44dd-4f2e-8539-2313c33bd7c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_e7013a69-e9b9-4e52-84dd-a87081174422" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_AccountsPayableCurrent_e7013a69-e9b9-4e52-84dd-a87081174422" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_81c6b934-0001-404a-99c2-713133ba0109" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_81c6b934-0001-404a-99c2-713133ba0109" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeCurrent_c018fd50-7a08-4951-9109-a7850555af2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_DeferredIncomeCurrent_c018fd50-7a08-4951-9109-a7850555af2a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesCurrent_e6827170-8f31-4986-b008-0549cf37e2bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedIncomeTaxesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_AccruedIncomeTaxesCurrent_e6827170-8f31-4986-b008-0549cf37e2bd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_IncomeTaxesCurrentPayableAndDeferredTaxLiabilities_81f26796-0d86-49e3-828d-4812e6262145" xlink:href="acmr-20250930.xsd#acmr_IncomeTaxesCurrentPayableAndDeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_acmr_IncomeTaxesCurrentPayableAndDeferredTaxLiabilities_81f26796-0d86-49e3-828d-4812e6262145" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccountsPayableAndAccruedLiabilities_648085b0-2e27-46c9-b3d2-aa64693c0eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAccountsPayableAndAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_OtherAccountsPayableAndAccruedLiabilities_648085b0-2e27-46c9-b3d2-aa64693c0eb6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_f1a8931f-7643-48e4-8154-2a962903e011" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_f1a8931f-7643-48e4-8154-2a962903e011" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_14f50587-2cd9-430c-b06f-d5247a223680" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_1ebf0248-431b-45a3-877c-df5b9fcaa582" xlink:to="loc_us-gaap_LiabilitiesCurrent_14f50587-2cd9-430c-b06f-d5247a223680" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_1093dc71-8f11-4e88-bd0d-44ae027dbde3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_1093dc71-8f11-4e88-bd0d-44ae027dbde3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_1bbb33a9-1213-498f-93f1-23b610585092" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_1bbb33a9-1213-498f-93f1-23b610585092" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_f8be701e-0edb-47e7-9267-f378ba8ef292" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_f8be701e-0edb-47e7-9267-f378ba8ef292" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_9ee3970f-a97c-450a-9fb7-05e6fdc9ae98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_Liabilities_9ee3970f-a97c-450a-9fb7-05e6fdc9ae98" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_3d51319c-bbbf-4e99-8bbd-7df17e43ac3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_CommitmentsAndContingencies_3d51319c-bbbf-4e99-8bbd-7df17e43ac3c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_040f0a4f-93cb-4f4b-89de-81001f917b1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_StockholdersEquityAbstract_040f0a4f-93cb-4f4b-89de-81001f917b1f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_040f0a4f-93cb-4f4b-89de-81001f917b1f" xlink:to="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_63ab9672-c232-4c3f-8a8e-6333746cc13b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:to="loc_us-gaap_CommonStockValue_63ab9672-c232-4c3f-8a8e-6333746cc13b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_25b34d7e-5234-4ab3-9e53-7fc85d9b2159" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:to="loc_us-gaap_AdditionalPaidInCapital_25b34d7e-5234-4ab3-9e53-7fc85d9b2159" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1ebaeee3-47d4-406f-9248-325776fdbc4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1ebaeee3-47d4-406f-9248-325776fdbc4d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance_432500b4-1499-4d00-ad13-4975c26a8c1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:to="loc_us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance_432500b4-1499-4d00-ad13-4975c26a8c1b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_7036aa08-02ef-40f7-bb4b-45b5082448c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_7036aa08-02ef-40f7-bb4b-45b5082448c9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_3cb63b3f-534f-4c65-8582-fbc89608d1f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_ddd3c5b5-17b2-4bbb-b524-71eb71f2e99e" xlink:to="loc_us-gaap_StockholdersEquity_3cb63b3f-534f-4c65-8582-fbc89608d1f5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_37acb77f-f6f7-4752-9530-0066a1c78217" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_040f0a4f-93cb-4f4b-89de-81001f917b1f" xlink:to="loc_us-gaap_MinorityInterest_37acb77f-f6f7-4752-9530-0066a1c78217" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_df2940d4-c681-4e6c-b871-1cc9d6e925d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_040f0a4f-93cb-4f4b-89de-81001f917b1f" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_df2940d4-c681-4e6c-b871-1cc9d6e925d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_f483df2a-115f-44d5-a316-a492e598fa04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_c7cf06ec-9be9-4144-be0d-ccdbacff1f9c" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_f483df2a-115f-44d5-a316-a492e598fa04" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/CondensedConsolidatedStatementsofComprehensiveIncomeParenthetical" xlink:type="simple" xlink:href="acmr-20250930.xsd#CondensedConsolidatedStatementsofComprehensiveIncomeParenthetical"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/CondensedConsolidatedStatementsofComprehensiveIncomeParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_50e8ae0a-d29a-4f72-bf9e-bf898016e529" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_a0802676-1163-44be-8727-8f550213432d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_50e8ae0a-d29a-4f72-bf9e-bf898016e529" xlink:to="loc_us-gaap_StatementTable_a0802676-1163-44be-8727-8f550213432d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_601ad0eb-c5d4-4818-aa8d-10c8cb2afe3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_a0802676-1163-44be-8727-8f550213432d" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_601ad0eb-c5d4-4818-aa8d-10c8cb2afe3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_601ad0eb-c5d4-4818-aa8d-10c8cb2afe3b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_601ad0eb-c5d4-4818-aa8d-10c8cb2afe3b" xlink:to="loc_us-gaap_RelatedPartyDomain_601ad0eb-c5d4-4818-aa8d-10c8cb2afe3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_02542bc1-d720-4d5d-8419-00957835d746" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_601ad0eb-c5d4-4818-aa8d-10c8cb2afe3b" xlink:to="loc_us-gaap_RelatedPartyDomain_02542bc1-d720-4d5d-8419-00957835d746" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_28a492b8-3fda-469e-b7e4-ffd28c431783" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_02542bc1-d720-4d5d-8419-00957835d746" xlink:to="loc_us-gaap_RelatedPartyMember_28a492b8-3fda-469e-b7e4-ffd28c431783" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_85042b0b-5c91-4221-84a7-218fbc0d618a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_50e8ae0a-d29a-4f72-bf9e-bf898016e529" xlink:to="loc_us-gaap_CostOfRevenue_85042b0b-5c91-4221-84a7-218fbc0d618a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_b8f8db2a-fcbf-4909-9658-81dc90d10a4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_50e8ae0a-d29a-4f72-bf9e-bf898016e529" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_b8f8db2a-fcbf-4909-9658-81dc90d10a4b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/CondensedConsolidatedStatementsofChangesinEquity" xlink:type="simple" xlink:href="acmr-20250930.xsd#CondensedConsolidatedStatementsofChangesinEquity"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/CondensedConsolidatedStatementsofChangesinEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ae003b78-a0cc-4fac-9012-8e6dbd9e4ccb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_e956bdba-60b6-42d1-b4a4-61ca991a78c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ae003b78-a0cc-4fac-9012-8e6dbd9e4ccb" xlink:to="loc_us-gaap_StatementTable_e956bdba-60b6-42d1-b4a4-61ca991a78c8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_822a6784-8448-4cbd-be04-b9ff183d40a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_e956bdba-60b6-42d1-b4a4-61ca991a78c8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_822a6784-8448-4cbd-be04-b9ff183d40a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_822a6784-8448-4cbd-be04-b9ff183d40a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_822a6784-8448-4cbd-be04-b9ff183d40a3" xlink:to="loc_us-gaap_EquityComponentDomain_822a6784-8448-4cbd-be04-b9ff183d40a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_822a6784-8448-4cbd-be04-b9ff183d40a3" xlink:to="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_c733172d-c008-4ed6-a808-619bd7f6b62b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:to="loc_us-gaap_CommonStockMember_c733172d-c008-4ed6-a808-619bd7f6b62b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_18852dee-b7eb-42ae-8706-f75ac2f1dad1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_18852dee-b7eb-42ae-8706-f75ac2f1dad1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_439d76e4-3a39-40d3-abb8-b2b3dbbc4672" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:to="loc_us-gaap_RetainedEarningsMember_439d76e4-3a39-40d3-abb8-b2b3dbbc4672" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAppropriatedMember_f01d3e0b-55ba-4757-a8ee-4bef01cb864a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAppropriatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:to="loc_us-gaap_RetainedEarningsAppropriatedMember_f01d3e0b-55ba-4757-a8ee-4bef01cb864a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_d56095a6-32df-4c1b-9f08-055619a34b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_d56095a6-32df-4c1b-9f08-055619a34b0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_abca906d-a518-40ec-8ba5-5c9328ad93fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_a1039580-0918-4c33-ab1d-dc8dce625249" xlink:to="loc_us-gaap_NoncontrollingInterestMember_abca906d-a518-40ec-8ba5-5c9328ad93fd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_45a6f265-3339-48fd-8ca4-730d84187b29" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_e956bdba-60b6-42d1-b4a4-61ca991a78c8" xlink:to="loc_us-gaap_StatementClassOfStockAxis_45a6f265-3339-48fd-8ca4-730d84187b29" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_45a6f265-3339-48fd-8ca4-730d84187b29_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_45a6f265-3339-48fd-8ca4-730d84187b29" xlink:to="loc_us-gaap_ClassOfStockDomain_45a6f265-3339-48fd-8ca4-730d84187b29_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_02cb304e-7fb3-4b47-93d0-1e79cc2c6ffa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_45a6f265-3339-48fd-8ca4-730d84187b29" xlink:to="loc_us-gaap_ClassOfStockDomain_02cb304e-7fb3-4b47-93d0-1e79cc2c6ffa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_edfed514-8264-468c-b771-ec07e273d597" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_02cb304e-7fb3-4b47-93d0-1e79cc2c6ffa" xlink:to="loc_us-gaap_CommonClassAMember_edfed514-8264-468c-b771-ec07e273d597" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_3a5bbc44-7b04-489f-9028-724e7038f633" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_02cb304e-7fb3-4b47-93d0-1e79cc2c6ffa" xlink:to="loc_us-gaap_CommonClassBMember_3a5bbc44-7b04-489f-9028-724e7038f633" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ae003b78-a0cc-4fac-9012-8e6dbd9e4ccb" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_d163cd45-7fae-4ba0-b510-a11b2ac75490" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_d163cd45-7fae-4ba0-b510-a11b2ac75490" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_cba58d7f-53b9-4904-b656-ee4e9f9e7777" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_cba58d7f-53b9-4904-b656-ee4e9f9e7777" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_a2c8ed00-35fa-4e60-af09-cea5d7bc284d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_ProfitLoss_a2c8ed00-35fa-4e60-af09-cea5d7bc284d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_0e9ffb74-05e4-4f82-b039-3856f1f6e2ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_0e9ffb74-05e4-4f82-b039-3856f1f6e2ec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_c995a4db-c57c-482b-ab10-8c1e5bd6f5ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_c995a4db-c57c-482b-ab10-8c1e5bd6f5ba" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_bb97f402-c2a4-44ea-afcc-965ea2ad2ae1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_bb97f402-c2a4-44ea-afcc-965ea2ad2ae1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_041b34b5-2076-410e-9576-4fa3dfd0b4f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_041b34b5-2076-410e-9576-4fa3dfd0b4f4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_6853abc3-b592-47c9-b564-c894f498b642" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_6853abc3-b592-47c9-b564-c894f498b642" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c9559863-f81d-45ea-bc52-3946bc39c7d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c9559863-f81d-45ea-bc52-3946bc39c7d0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_b6d568d1-a68a-4fcd-bfef-3c417da8569d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_b6d568d1-a68a-4fcd-bfef-3c417da8569d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_740292f4-64e8-4fb5-a173-d31b1480cb7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_740292f4-64e8-4fb5-a173-d31b1480cb7f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_1657e808-fc67-4ec5-b089-ca0dea449915" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_729e4d8a-07e8-4a54-ba99-eee9df52b76c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_1657e808-fc67-4ec5-b089-ca0dea449915" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_1725a6b3-2e77-4d26-8e7c-a310ef0bb102" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_17c788c4-bc8b-4ed2-bde3-e58b5934e63a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/DESCRIPTIONOFBUSINESSNarrativeDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#DESCRIPTIONOFBUSINESSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/DESCRIPTIONOFBUSINESSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_7822ec24-3adf-4d25-92c9-00c8f7524c22" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_91788e1c-a6d1-4a16-938d-9b7becca0230" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_7822ec24-3adf-4d25-92c9-00c8f7524c22" xlink:to="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_91788e1c-a6d1-4a16-938d-9b7becca0230" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_948c65db-b51b-4c1a-96ad-fb35d7f098cc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_91788e1c-a6d1-4a16-938d-9b7becca0230" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_948c65db-b51b-4c1a-96ad-fb35d7f098cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_948c65db-b51b-4c1a-96ad-fb35d7f098cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_948c65db-b51b-4c1a-96ad-fb35d7f098cc" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_948c65db-b51b-4c1a-96ad-fb35d7f098cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_46cd9468-db34-4498-a823-58fbeb7133dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_948c65db-b51b-4c1a-96ad-fb35d7f098cc" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_46cd9468-db34-4498-a823-58fbeb7133dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_PrivateOfferingMember_706ac9e7-7a12-4c70-bedc-de2ac1db0422" xlink:href="acmr-20250930.xsd#acmr_PrivateOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_46cd9468-db34-4498-a823-58fbeb7133dd" xlink:to="loc_acmr_PrivateOfferingMember_706ac9e7-7a12-4c70-bedc-de2ac1db0422" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_7b0cdb37-72d6-4b69-aacf-faa16c4266b5" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_91788e1c-a6d1-4a16-938d-9b7becca0230" xlink:to="loc_srt_ConsolidatedEntitiesAxis_7b0cdb37-72d6-4b69-aacf-faa16c4266b5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_7b0cdb37-72d6-4b69-aacf-faa16c4266b5_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_7b0cdb37-72d6-4b69-aacf-faa16c4266b5" xlink:to="loc_srt_ConsolidatedEntitiesDomain_7b0cdb37-72d6-4b69-aacf-faa16c4266b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_0b051aef-63e3-46dc-8fb4-021711a29a82" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_7b0cdb37-72d6-4b69-aacf-faa16c4266b5" xlink:to="loc_srt_ConsolidatedEntitiesDomain_0b051aef-63e3-46dc-8fb4-021711a29a82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchShanghaiIncMember_b9a81da1-97cc-4041-a7b4-d3633d7e2783" xlink:href="acmr-20250930.xsd#acmr_ACMResearchShanghaiIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_0b051aef-63e3-46dc-8fb4-021711a29a82" xlink:to="loc_acmr_ACMResearchShanghaiIncMember_b9a81da1-97cc-4041-a7b4-d3633d7e2783" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_94f1b87a-aa74-4892-be90-5cf24d66cde9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_7822ec24-3adf-4d25-92c9-00c8f7524c22" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_94f1b87a-aa74-4892-be90-5cf24d66cde9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_SubsidiariesOwnershipPercentage_e2661ce4-ad73-4ab3-833d-ab0f2195bc8c" xlink:href="acmr-20250930.xsd#acmr_SubsidiariesOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_7822ec24-3adf-4d25-92c9-00c8f7524c22" xlink:to="loc_acmr_SubsidiariesOwnershipPercentage_e2661ce4-ad73-4ab3-833d-ab0f2195bc8c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/DESCRIPTIONOFBUSINESSDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#DESCRIPTIONOFBUSINESSDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/DESCRIPTIONOFBUSINESSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_5c07d20f-c8b3-4350-94d8-f379aa5e0991" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_1eba60e3-0aa2-4eab-bda9-e67e16039220" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_5c07d20f-c8b3-4350-94d8-f379aa5e0991" xlink:to="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_1eba60e3-0aa2-4eab-bda9-e67e16039220" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_b1ccb4b0-41cc-4867-a347-060655bce732" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_1eba60e3-0aa2-4eab-bda9-e67e16039220" xlink:to="loc_srt_ConsolidatedEntitiesAxis_b1ccb4b0-41cc-4867-a347-060655bce732" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_b1ccb4b0-41cc-4867-a347-060655bce732_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_b1ccb4b0-41cc-4867-a347-060655bce732" xlink:to="loc_srt_ConsolidatedEntitiesDomain_b1ccb4b0-41cc-4867-a347-060655bce732_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_b1ccb4b0-41cc-4867-a347-060655bce732" xlink:to="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchShanghaiIncMember_36d4c070-d920-44a4-a8ea-8f1424c4fffe" xlink:href="acmr-20250930.xsd#acmr_ACMResearchShanghaiIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchShanghaiIncMember_36d4c070-d920-44a4-a8ea-8f1424c4fffe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchWuxiIncMember_e587ac66-8fe1-44b4-887f-76e7fe4e1a91" xlink:href="acmr-20250930.xsd#acmr_ACMResearchWuxiIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchWuxiIncMember_e587ac66-8fe1-44b4-887f-76e7fe4e1a91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CleanChipTechnologiesLimitedMember_763a836d-27d4-4d42-b270-070b30e718a3" xlink:href="acmr-20250930.xsd#acmr_CleanChipTechnologiesLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_CleanChipTechnologiesLimitedMember_763a836d-27d4-4d42-b270-070b30e718a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchKoreaCOLTDMember_c7c2c4bf-a800-4838-b2ea-3d8b637977db" xlink:href="acmr-20250930.xsd#acmr_ACMResearchKoreaCOLTDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchKoreaCOLTDMember_c7c2c4bf-a800-4838-b2ea-3d8b637977db" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchLingangInc.ACMLingangMember_8849e4d9-1834-4fa9-8742-f780abccff6b" xlink:href="acmr-20250930.xsd#acmr_ACMResearchLingangInc.ACMLingangMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchLingangInc.ACMLingangMember_8849e4d9-1834-4fa9-8742-f780abccff6b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchCAIncMember_b2615ca1-09ee-45e8-aef2-5f0b18482b2b" xlink:href="acmr-20250930.xsd#acmr_ACMResearchCAIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchCAIncMember_b2615ca1-09ee-45e8-aef2-5f0b18482b2b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchCaymanIncMember_c980da0c-37d9-444b-9435-7858a1622172" xlink:href="acmr-20250930.xsd#acmr_ACMResearchCaymanIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchCaymanIncMember_c980da0c-37d9-444b-9435-7858a1622172" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchSingaporePTELTDMember_aa84f8b5-f11b-4a67-9902-5116e5e98819" xlink:href="acmr-20250930.xsd#acmr_ACMResearchSingaporePTELTDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchSingaporePTELTDMember_aa84f8b5-f11b-4a67-9902-5116e5e98819" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchBeijingIncMember_56b69733-c2be-41ef-b1db-a95e51fddd74" xlink:href="acmr-20250930.xsd#acmr_ACMResearchBeijingIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchBeijingIncMember_56b69733-c2be-41ef-b1db-a95e51fddd74" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_HangukACMCOLTDMember_547cf1bb-b801-4986-8baf-7913ee7d96d1" xlink:href="acmr-20250930.xsd#acmr_HangukACMCOLTDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_HangukACMCOLTDMember_547cf1bb-b801-4986-8baf-7913ee7d96d1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMWooliMicroelectronicsShanghaiCoLtdMember_504485ef-1ac0-465a-b4d9-b640da541d1f" xlink:href="acmr-20250930.xsd#acmr_ACMWooliMicroelectronicsShanghaiCoLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMWooliMicroelectronicsShanghaiCoLtdMember_504485ef-1ac0-465a-b4d9-b640da541d1f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchChengduInc.Member_0a57ed3a-162b-40cf-8eab-d9d06784db9b" xlink:href="acmr-20250930.xsd#acmr_ACMResearchChengduInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ACMResearchChengduInc.Member_0a57ed3a-162b-40cf-8eab-d9d06784db9b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ShengyiMicroSemiconductorShanghaiCo.Ltd.Member_8b56982e-6f23-49e8-ba87-1c669c7f819d" xlink:href="acmr-20250930.xsd#acmr_ShengyiMicroSemiconductorShanghaiCo.Ltd.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_ShengyiMicroSemiconductorShanghaiCo.Ltd.Member_8b56982e-6f23-49e8-ba87-1c669c7f819d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_YushengMicroSemiconductorShanghaiCoLtdMember_e599c873-bf00-48f0-8f39-e8c92824c742" xlink:href="acmr-20250930.xsd#acmr_YushengMicroSemiconductorShanghaiCoLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_3f6a29bb-8655-4bf0-b572-a0b84ff4264c" xlink:to="loc_acmr_YushengMicroSemiconductorShanghaiCoLtdMember_e599c873-bf00-48f0-8f39-e8c92824c742" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_BusinessDescriptionAbstract_588c9cae-b34c-4081-ad14-eb80aceb2b29" xlink:href="acmr-20250930.xsd#acmr_BusinessDescriptionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_5c07d20f-c8b3-4350-94d8-f379aa5e0991" xlink:to="loc_acmr_BusinessDescriptionAbstract_588c9cae-b34c-4081-ad14-eb80aceb2b29" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_SubsidiariesOwnershipPercentage_0cd6c43d-4dd3-4d83-b66b-50776acfbd83" xlink:href="acmr-20250930.xsd#acmr_SubsidiariesOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_BusinessDescriptionAbstract_588c9cae-b34c-4081-ad14-eb80aceb2b29" xlink:to="loc_acmr_SubsidiariesOwnershipPercentage_0cd6c43d-4dd3-4d83-b66b-50776acfbd83" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESCashandCashEquivalentsDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESCashandCashEquivalentsDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESCashandCashEquivalentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsLineItems_6d4f3c94-de27-42bb-88ec-c05d61fdd946" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_7ca2e3eb-af4a-4eca-9ef4-1e371a235c7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfCashAndCashEquivalentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_6d4f3c94-de27-42bb-88ec-c05d61fdd946" xlink:to="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_7ca2e3eb-af4a-4eca-9ef4-1e371a235c7b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_5067e77d-9901-4179-b2b2-70941f84b9fd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_7ca2e3eb-af4a-4eca-9ef4-1e371a235c7b" xlink:to="loc_srt_StatementGeographicalAxis_5067e77d-9901-4179-b2b2-70941f84b9fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_5067e77d-9901-4179-b2b2-70941f84b9fd_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_5067e77d-9901-4179-b2b2-70941f84b9fd" xlink:to="loc_srt_SegmentGeographicalDomain_5067e77d-9901-4179-b2b2-70941f84b9fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_3de1e376-4f19-48fe-99f4-d0f2d6fcd936" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_5067e77d-9901-4179-b2b2-70941f84b9fd" xlink:to="loc_srt_SegmentGeographicalDomain_3de1e376-4f19-48fe-99f4-d0f2d6fcd936" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_a3c1ed50-bca0-4a24-80d7-48f27d972918" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3de1e376-4f19-48fe-99f4-d0f2d6fcd936" xlink:to="loc_country_US_a3c1ed50-bca0-4a24-80d7-48f27d972918" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_3735a7fc-a165-461a-9633-9da018d8a0fb" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3de1e376-4f19-48fe-99f4-d0f2d6fcd936" xlink:to="loc_country_CN_3735a7fc-a165-461a-9633-9da018d8a0fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_HK_4040c41b-a530-4cfc-91d9-eac10c82a9c8" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_HK"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3de1e376-4f19-48fe-99f4-d0f2d6fcd936" xlink:to="loc_country_HK_4040c41b-a530-4cfc-91d9-eac10c82a9c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_KR_edaac85c-80dc-44b9-bab7-5b82f8d6e2e2" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_KR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3de1e376-4f19-48fe-99f4-d0f2d6fcd936" xlink:to="loc_country_KR_edaac85c-80dc-44b9-bab7-5b82f8d6e2e2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_SG_c560cec7-8bf3-4348-9eb4-0bd95eba8ab4" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_SG"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3de1e376-4f19-48fe-99f4-d0f2d6fcd936" xlink:to="loc_country_SG_c560cec7-8bf3-4348-9eb4-0bd95eba8ab4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_f73e771e-d39c-4261-9394-61599c744d09" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCashAndCashEquivalentsTable_7ca2e3eb-af4a-4eca-9ef4-1e371a235c7b" xlink:to="loc_srt_ConsolidatedEntitiesAxis_f73e771e-d39c-4261-9394-61599c744d09" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_f73e771e-d39c-4261-9394-61599c744d09_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_f73e771e-d39c-4261-9394-61599c744d09" xlink:to="loc_srt_ConsolidatedEntitiesDomain_f73e771e-d39c-4261-9394-61599c744d09_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_646bf91e-6c95-4fea-b587-8cf36ec5163a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_f73e771e-d39c-4261-9394-61599c744d09" xlink:to="loc_srt_ConsolidatedEntitiesDomain_646bf91e-6c95-4fea-b587-8cf36ec5163a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMShanghaiMember_e26a6123-ad58-4fa9-8f1d-af4018f834bf" xlink:href="acmr-20250930.xsd#acmr_ACMShanghaiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_646bf91e-6c95-4fea-b587-8cf36ec5163a" xlink:to="loc_acmr_ACMShanghaiMember_e26a6123-ad58-4fa9-8f1d-af4018f834bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_48821c27-7874-49ff-a65c-4f7ae38ac752" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_6d4f3c94-de27-42bb-88ec-c05d61fdd946" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_48821c27-7874-49ff-a65c-4f7ae38ac752" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CashCashEquivalentsAndRestrictedCashAndTimeDeposits_61d1361b-7710-4ae4-ac20-027a317fefcc" xlink:href="acmr-20250930.xsd#acmr_CashCashEquivalentsAndRestrictedCashAndTimeDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_48821c27-7874-49ff-a65c-4f7ae38ac752" xlink:to="loc_acmr_CashCashEquivalentsAndRestrictedCashAndTimeDeposits_61d1361b-7710-4ae4-ac20-027a317fefcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositAssets_7bcaf5b4-af72-4172-a463-5e8c456611d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepositAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_48821c27-7874-49ff-a65c-4f7ae38ac752" xlink:to="loc_us-gaap_DepositAssets_7bcaf5b4-af72-4172-a463-5e8c456611d8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToSuppliersAndEmployees_43693b0d-be26-4762-90d0-6b47660f5b9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToSuppliersAndEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_48821c27-7874-49ff-a65c-4f7ae38ac752" xlink:to="loc_us-gaap_PaymentsToSuppliersAndEmployees_43693b0d-be26-4762-90d0-6b47660f5b9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfOrdinaryDividends_5524559c-40dd-4af2-a96b-d2e7add25188" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfOrdinaryDividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_6d4f3c94-de27-42bb-88ec-c05d61fdd946" xlink:to="loc_us-gaap_PaymentsOfOrdinaryDividends_5524559c-40dd-4af2-a96b-d2e7add25188" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividendsMinorityInterest_43a76827-59f3-4498-a1ca-9b844663e080" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDividendsMinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsLineItems_6d4f3c94-de27-42bb-88ec-c05d61fdd946" xlink:to="loc_us-gaap_PaymentsOfDividendsMinorityInterest_43a76827-59f3-4498-a1ca-9b844663e080" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSummaryofFairValueDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSummaryofFairValueDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSummaryofFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00b27392-4107-4b11-8db4-b7ef1de8ee1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_103a9fe8-964f-45fe-abc8-a824622fcb25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00b27392-4107-4b11-8db4-b7ef1de8ee1f" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_103a9fe8-964f-45fe-abc8-a824622fcb25" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_cdb4cdf9-2da1-4bf1-ac43-2e7f6cf077ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_103a9fe8-964f-45fe-abc8-a824622fcb25" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_cdb4cdf9-2da1-4bf1-ac43-2e7f6cf077ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_cdb4cdf9-2da1-4bf1-ac43-2e7f6cf077ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_cdb4cdf9-2da1-4bf1-ac43-2e7f6cf077ce" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_cdb4cdf9-2da1-4bf1-ac43-2e7f6cf077ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_539ac782-9706-41ac-93b6-9d512ecd954e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_cdb4cdf9-2da1-4bf1-ac43-2e7f6cf077ce" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_539ac782-9706-41ac-93b6-9d512ecd954e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_af8e99a1-5576-4d5e-b64b-a152ec31cc71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_539ac782-9706-41ac-93b6-9d512ecd954e" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_af8e99a1-5576-4d5e-b64b-a152ec31cc71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_1aeda2b5-ed78-4709-8f22-edff65d0ab95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_539ac782-9706-41ac-93b6-9d512ecd954e" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_1aeda2b5-ed78-4709-8f22-edff65d0ab95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_c3b9156a-787b-40fa-9a10-3020bddab91d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_539ac782-9706-41ac-93b6-9d512ecd954e" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_c3b9156a-787b-40fa-9a10-3020bddab91d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45d67b21-cd2b-475a-aea8-22f9a59d708a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_103a9fe8-964f-45fe-abc8-a824622fcb25" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45d67b21-cd2b-475a-aea8-22f9a59d708a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_45d67b21-cd2b-475a-aea8-22f9a59d708a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45d67b21-cd2b-475a-aea8-22f9a59d708a" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_45d67b21-cd2b-475a-aea8-22f9a59d708a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_714d46f2-3dc7-46f6-8084-384f78a1c3d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45d67b21-cd2b-475a-aea8-22f9a59d708a" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_714d46f2-3dc7-46f6-8084-384f78a1c3d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_be785f17-558e-473a-81d3-2d5fd1f9d823" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_714d46f2-3dc7-46f6-8084-384f78a1c3d9" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_be785f17-558e-473a-81d3-2d5fd1f9d823" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_4d39daa6-bddf-4fd9-b74f-7d281fefc217" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00b27392-4107-4b11-8db4-b7ef1de8ee1f" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_4d39daa6-bddf-4fd9-b74f-7d281fefc217" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_05d35172-2281-4cd8-b9c2-61e22f121484" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_4d39daa6-bddf-4fd9-b74f-7d281fefc217" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_05d35172-2281-4cd8-b9c2-61e22f121484" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingSecurities_09ce131b-451c-41b9-8513-61434d251ac1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradingSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_4d39daa6-bddf-4fd9-b74f-7d281fefc217" xlink:to="loc_us-gaap_TradingSecurities_09ce131b-451c-41b9-8513-61434d251ac1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_85f54da4-e938-4630-b183-eeb9ab31321f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_4d39daa6-bddf-4fd9-b74f-7d281fefc217" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_85f54da4-e938-4630-b183-eeb9ab31321f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_93bd8b25-2226-4d4e-8beb-938b8852d7e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_4d39daa6-bddf-4fd9-b74f-7d281fefc217" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_93bd8b25-2226-4d4e-8beb-938b8852d7e8" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESConcentrationofCreditRiskDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESConcentrationofCreditRiskDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESConcentrationofCreditRiskDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_5bc325cc-0d9d-48f3-bb24-83c93ead9947" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_f79b7174-6fc5-4e2a-b100-e86f36a27acd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_5bc325cc-0d9d-48f3-bb24-83c93ead9947" xlink:to="loc_us-gaap_ConcentrationRiskTable_f79b7174-6fc5-4e2a-b100-e86f36a27acd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_190278f6-ad39-43c5-be39-f7eb858e55ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_f79b7174-6fc5-4e2a-b100-e86f36a27acd" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_190278f6-ad39-43c5-be39-f7eb858e55ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_190278f6-ad39-43c5-be39-f7eb858e55ff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_190278f6-ad39-43c5-be39-f7eb858e55ff" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_190278f6-ad39-43c5-be39-f7eb858e55ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_2e325674-48eb-48b8-aed3-91db94c6c662" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_190278f6-ad39-43c5-be39-f7eb858e55ff" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_2e325674-48eb-48b8-aed3-91db94c6c662" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_efff88cf-5d5a-48b6-9c33-1d4fc6d8dce1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_2e325674-48eb-48b8-aed3-91db94c6c662" xlink:to="loc_us-gaap_SalesRevenueNetMember_efff88cf-5d5a-48b6-9c33-1d4fc6d8dce1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_2c5be65c-1ae0-42a4-9ff9-1eef5e8765a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_2e325674-48eb-48b8-aed3-91db94c6c662" xlink:to="loc_us-gaap_AccountsReceivableMember_2c5be65c-1ae0-42a4-9ff9-1eef5e8765a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_a16fbfe0-3f85-483a-9ce4-62811b794251" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_f79b7174-6fc5-4e2a-b100-e86f36a27acd" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_a16fbfe0-3f85-483a-9ce4-62811b794251" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_a16fbfe0-3f85-483a-9ce4-62811b794251_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_a16fbfe0-3f85-483a-9ce4-62811b794251" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_a16fbfe0-3f85-483a-9ce4-62811b794251_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_46e4fda2-1ed6-4b52-9671-d237cc8c1758" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_a16fbfe0-3f85-483a-9ce4-62811b794251" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_46e4fda2-1ed6-4b52-9671-d237cc8c1758" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_81d98e6c-22e2-4a98-875b-a109c8720195" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_46e4fda2-1ed6-4b52-9671-d237cc8c1758" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_81d98e6c-22e2-4a98-875b-a109c8720195" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_1ea08913-6477-465d-ab0c-7cf24efeb994" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_f79b7174-6fc5-4e2a-b100-e86f36a27acd" xlink:to="loc_srt_MajorCustomersAxis_1ea08913-6477-465d-ab0c-7cf24efeb994" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_1ea08913-6477-465d-ab0c-7cf24efeb994_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_1ea08913-6477-465d-ab0c-7cf24efeb994" xlink:to="loc_srt_NameOfMajorCustomerDomain_1ea08913-6477-465d-ab0c-7cf24efeb994_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_c123ae05-70e3-40c7-bd38-f301df8464d1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_1ea08913-6477-465d-ab0c-7cf24efeb994" xlink:to="loc_srt_NameOfMajorCustomerDomain_c123ae05-70e3-40c7-bd38-f301df8464d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_TwoCustomersMember_0c55e0dd-c5d9-4c84-9fef-70f24d6af101" xlink:href="acmr-20250930.xsd#acmr_TwoCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_c123ae05-70e3-40c7-bd38-f301df8464d1" xlink:to="loc_acmr_TwoCustomersMember_0c55e0dd-c5d9-4c84-9fef-70f24d6af101" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_FourCustomersMember_8c0f46af-e717-43dd-9a8b-34d1c8a88e22" xlink:href="acmr-20250930.xsd#acmr_FourCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_c123ae05-70e3-40c7-bd38-f301df8464d1" xlink:to="loc_acmr_FourCustomersMember_8c0f46af-e717-43dd-9a8b-34d1c8a88e22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_FiveCustomersMember_b79280f8-9b1b-49d1-aaa1-bc2f2b0f188c" xlink:href="acmr-20250930.xsd#acmr_FiveCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_c123ae05-70e3-40c7-bd38-f301df8464d1" xlink:to="loc_acmr_FiveCustomersMember_b79280f8-9b1b-49d1-aaa1-bc2f2b0f188c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ConcentrationOfCreditRiskAbstract_f9a577c0-7e26-455c-a0bf-b8017b5088d6" xlink:href="acmr-20250930.xsd#acmr_ConcentrationOfCreditRiskAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_5bc325cc-0d9d-48f3-bb24-83c93ead9947" xlink:to="loc_acmr_ConcentrationOfCreditRiskAbstract_f9a577c0-7e26-455c-a0bf-b8017b5088d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_201e76b6-872c-44c5-8b91-893b88e1b84f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_ConcentrationOfCreditRiskAbstract_f9a577c0-7e26-455c-a0bf-b8017b5088d6" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_201e76b6-872c-44c5-8b91-893b88e1b84f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSDisaggregatedRevenueDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#REVENUEFROMCONTRACTSWITHCUSTOMERSDisaggregatedRevenueDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/REVENUEFROMCONTRACTSWITHCUSTOMERSDisaggregatedRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_265d9f2f-02da-4075-8594-bb3442d15e4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_dc1a5eb4-66fa-40bf-b6e6-ea77f38b8b07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_265d9f2f-02da-4075-8594-bb3442d15e4b" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_dc1a5eb4-66fa-40bf-b6e6-ea77f38b8b07" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_47d30097-8901-4713-8e0c-dcdc17b5d43f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_dc1a5eb4-66fa-40bf-b6e6-ea77f38b8b07" xlink:to="loc_srt_ProductOrServiceAxis_47d30097-8901-4713-8e0c-dcdc17b5d43f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_47d30097-8901-4713-8e0c-dcdc17b5d43f_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_47d30097-8901-4713-8e0c-dcdc17b5d43f" xlink:to="loc_srt_ProductsAndServicesDomain_47d30097-8901-4713-8e0c-dcdc17b5d43f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d5f984d0-ffa5-4c36-a29c-01f628a8b2cd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_47d30097-8901-4713-8e0c-dcdc17b5d43f" xlink:to="loc_srt_ProductsAndServicesDomain_d5f984d0-ffa5-4c36-a29c-01f628a8b2cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_TotalSingleWaferAndSemiCriticalCleaningEquipmentMember_806441dc-bac6-40dc-aad0-75e00d9e0140" xlink:href="acmr-20250930.xsd#acmr_TotalSingleWaferAndSemiCriticalCleaningEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d5f984d0-ffa5-4c36-a29c-01f628a8b2cd" xlink:to="loc_acmr_TotalSingleWaferAndSemiCriticalCleaningEquipmentMember_806441dc-bac6-40dc-aad0-75e00d9e0140" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ECPFrontEndAndPackagingFurnaceAndOtherTechnologiesMember_3caa62a1-0ecc-426c-835d-2cb6d8330e2e" xlink:href="acmr-20250930.xsd#acmr_ECPFrontEndAndPackagingFurnaceAndOtherTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d5f984d0-ffa5-4c36-a29c-01f628a8b2cd" xlink:to="loc_acmr_ECPFrontEndAndPackagingFurnaceAndOtherTechnologiesMember_3caa62a1-0ecc-426c-835d-2cb6d8330e2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_AdvancedPackagingExcludeECPServicesSparesMember_ce82a23f-28bd-4d60-875f-7527c55d6260" xlink:href="acmr-20250930.xsd#acmr_AdvancedPackagingExcludeECPServicesSparesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d5f984d0-ffa5-4c36-a29c-01f628a8b2cd" xlink:to="loc_acmr_AdvancedPackagingExcludeECPServicesSparesMember_ce82a23f-28bd-4d60-875f-7527c55d6260" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_DisaggregatedRevenueInformationAbstract_722748b4-810f-4dc2-93bf-f5ec67f35c25" xlink:href="acmr-20250930.xsd#acmr_DisaggregatedRevenueInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_265d9f2f-02da-4075-8594-bb3442d15e4b" xlink:to="loc_acmr_DisaggregatedRevenueInformationAbstract_722748b4-810f-4dc2-93bf-f5ec67f35c25" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a3bcb289-0174-49bb-98c5-a91363617469" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_DisaggregatedRevenueInformationAbstract_722748b4-810f-4dc2-93bf-f5ec67f35c25" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a3bcb289-0174-49bb-98c5-a91363617469" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/INVENTORIESNETDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#INVENTORIESNETDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/INVENTORIESNETDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryLineItems_497501ff-80ea-4443-b6df-1b93a0c9ac2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryCurrentTable_8f1a1d29-bf82-47b3-9c48-e84606573b9f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryCurrentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_InventoryLineItems_497501ff-80ea-4443-b6df-1b93a0c9ac2c" xlink:to="loc_us-gaap_InventoryCurrentTable_8f1a1d29-bf82-47b3-9c48-e84606573b9f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryAxis_4b534774-ddd2-4078-a114-9ace89b84a07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PublicUtilitiesInventoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InventoryCurrentTable_8f1a1d29-bf82-47b3-9c48-e84606573b9f" xlink:to="loc_us-gaap_PublicUtilitiesInventoryAxis_4b534774-ddd2-4078-a114-9ace89b84a07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_4b534774-ddd2-4078-a114-9ace89b84a07_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_4b534774-ddd2-4078-a114-9ace89b84a07" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_4b534774-ddd2-4078-a114-9ace89b84a07_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_d85df322-ce5c-4b1f-bc0f-d374ee100ffd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_4b534774-ddd2-4078-a114-9ace89b84a07" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_d85df322-ce5c-4b1f-bc0f-d374ee100ffd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_FirstToolsCustomerOwnershipMember_544af5c9-6e35-4714-93cc-6589ccc0fcd2" xlink:href="acmr-20250930.xsd#acmr_FirstToolsCustomerOwnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_d85df322-ce5c-4b1f-bc0f-d374ee100ffd" xlink:to="loc_acmr_FirstToolsCustomerOwnershipMember_544af5c9-6e35-4714-93cc-6589ccc0fcd2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNetAbstract_ac4cc801-4295-4757-8b5c-89a05b0b63d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_497501ff-80ea-4443-b6df-1b93a0c9ac2c" xlink:to="loc_us-gaap_InventoryNetAbstract_ac4cc801-4295-4757-8b5c-89a05b0b63d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryRawMaterials_60a337e3-ff91-4058-af2b-5cc655bcc86d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryRawMaterials"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryNetAbstract_ac4cc801-4295-4757-8b5c-89a05b0b63d2" xlink:to="loc_us-gaap_InventoryRawMaterials_60a337e3-ff91-4058-af2b-5cc655bcc86d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWorkInProcess_cbb33a3c-f3ca-496a-977e-6893705ec465" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryWorkInProcess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryNetAbstract_ac4cc801-4295-4757-8b5c-89a05b0b63d2" xlink:to="loc_us-gaap_InventoryWorkInProcess_cbb33a3c-f3ca-496a-977e-6893705ec465" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryFinishedGoods_9a31926f-9065-460c-b34c-2fca6648dfa2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryFinishedGoods"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryNetAbstract_ac4cc801-4295-4757-8b5c-89a05b0b63d2" xlink:to="loc_us-gaap_InventoryFinishedGoods_9a31926f-9065-460c-b34c-2fca6648dfa2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_d76b9afe-be63-4d1a-a432-1e2e0efd0b27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryNetAbstract_ac4cc801-4295-4757-8b5c-89a05b0b63d2" xlink:to="loc_us-gaap_InventoryGross_d76b9afe-be63-4d1a-a432-1e2e0efd0b27" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories_8037dcdb-f40d-414b-a4de-07cedb6a705a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_497501ff-80ea-4443-b6df-1b93a0c9ac2c" xlink:to="loc_us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories_8037dcdb-f40d-414b-a4de-07cedb6a705a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWriteDown_1631b449-1293-466f-95bc-7487083c949d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryWriteDown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_497501ff-80ea-4443-b6df-1b93a0c9ac2c" xlink:to="loc_us-gaap_InventoryWriteDown_1631b449-1293-466f-95bc-7487083c949d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/PROPERTYPLANTANDEQUIPMENTNETDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#PROPERTYPLANTANDEQUIPMENTNETDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/PROPERTYPLANTANDEQUIPMENTNETDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2feebab-b5cf-4246-ad72-69d743fb6472" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0b2e3c30-149f-48c1-af68-1978fa4ba991" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2feebab-b5cf-4246-ad72-69d743fb6472" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0b2e3c30-149f-48c1-af68-1978fa4ba991" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12186e67-ce15-4ee2-b678-c9b5cf923654" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0b2e3c30-149f-48c1-af68-1978fa4ba991" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12186e67-ce15-4ee2-b678-c9b5cf923654" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_12186e67-ce15-4ee2-b678-c9b5cf923654_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12186e67-ce15-4ee2-b678-c9b5cf923654" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_12186e67-ce15-4ee2-b678-c9b5cf923654_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_12186e67-ce15-4ee2-b678-c9b5cf923654" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_BuildingsAndPlantsMember_29d27759-0a9a-4301-9882-071f2ee1a562" xlink:href="acmr-20250930.xsd#acmr_BuildingsAndPlantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:to="loc_acmr_BuildingsAndPlantsMember_29d27759-0a9a-4301-9882-071f2ee1a562" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_f2ad3961-4444-440c-a532-114a03a0e8d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:to="loc_us-gaap_LandMember_f2ad3961-4444-440c-a532-114a03a0e8d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_ba9ea712-d522-441a-9c8c-2a5e7e012e96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:to="loc_us-gaap_EquipmentMember_ba9ea712-d522-441a-9c8c-2a5e7e012e96" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OfficeEquipmentMember_804eb15b-b117-435d-9502-560652d76342" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OfficeEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:to="loc_us-gaap_OfficeEquipmentMember_804eb15b-b117-435d-9502-560652d76342" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransportationEquipmentMember_3e6b6a7a-679c-4e07-8374-3c6a7d3c8950" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransportationEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:to="loc_us-gaap_TransportationEquipmentMember_3e6b6a7a-679c-4e07-8374-3c6a7d3c8950" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_6ac53da1-97bf-4b47-a8c9-31a3cb70c821" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1bd849c8-8f42-4889-a499-b8d6668be849" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_6ac53da1-97bf-4b47-a8c9-31a3cb70c821" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract_a83de766-06a4-441c-9609-2f14e62812b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b2feebab-b5cf-4246-ad72-69d743fb6472" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract_a83de766-06a4-441c-9609-2f14e62812b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_11f24812-8117-4583-b9a9-3dd9941e33b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract_a83de766-06a4-441c-9609-2f14e62812b6" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_11f24812-8117-4583-b9a9-3dd9941e33b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressGross_b51ecacd-5f81-4527-a472-d184b83f4782" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConstructionInProgressGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract_a83de766-06a4-441c-9609-2f14e62812b6" xlink:to="loc_us-gaap_ConstructionInProgressGross_b51ecacd-5f81-4527-a472-d184b83f4782" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_cc876001-476b-4a6a-88dc-02dbffe2f8d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract_a83de766-06a4-441c-9609-2f14e62812b6" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_cc876001-476b-4a6a-88dc-02dbffe2f8d6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_fbb1d889-cab5-4358-9790-1a32ea165688" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract_a83de766-06a4-441c-9609-2f14e62812b6" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_fbb1d889-cab5-4358-9790-1a32ea165688" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/PROPERTYPLANTANDEQUIPMENTNETNarrativeDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#PROPERTYPLANTANDEQUIPMENTNETNarrativeDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/PROPERTYPLANTANDEQUIPMENTNETNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c581340f-6bb5-4fa2-852a-4db662144d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2a3ee6a3-c319-4fc8-857d-4c15675e568f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c581340f-6bb5-4fa2-852a-4db662144d1b" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2a3ee6a3-c319-4fc8-857d-4c15675e568f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_824904fc-d361-46f1-884f-cc4769a1f219" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2a3ee6a3-c319-4fc8-857d-4c15675e568f" xlink:to="loc_srt_ConsolidatedEntitiesAxis_824904fc-d361-46f1-884f-cc4769a1f219" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_824904fc-d361-46f1-884f-cc4769a1f219_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_824904fc-d361-46f1-884f-cc4769a1f219" xlink:to="loc_srt_ConsolidatedEntitiesDomain_824904fc-d361-46f1-884f-cc4769a1f219_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_dd917dec-92cb-4bfd-9e03-6d098c9c5b13" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_824904fc-d361-46f1-884f-cc4769a1f219" xlink:to="loc_srt_ConsolidatedEntitiesDomain_dd917dec-92cb-4bfd-9e03-6d098c9c5b13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchLingangInc.ACMLingangMember_92395653-1e15-4079-8ded-33fd80407628" xlink:href="acmr-20250930.xsd#acmr_ACMResearchLingangInc.ACMLingangMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_dd917dec-92cb-4bfd-9e03-6d098c9c5b13" xlink:to="loc_acmr_ACMResearchLingangInc.ACMLingangMember_92395653-1e15-4079-8ded-33fd80407628" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bef21637-6fc1-4145-8e0e-4648f270ff02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2a3ee6a3-c319-4fc8-857d-4c15675e568f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bef21637-6fc1-4145-8e0e-4648f270ff02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_bef21637-6fc1-4145-8e0e-4648f270ff02_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bef21637-6fc1-4145-8e0e-4648f270ff02" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_bef21637-6fc1-4145-8e0e-4648f270ff02_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9a456d86-c6ed-4afc-b26a-1d1942598a1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bef21637-6fc1-4145-8e0e-4648f270ff02" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9a456d86-c6ed-4afc-b26a-1d1942598a1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LandBuildingsAndPlantsMember_47efd6a3-3dd8-49b6-9ec0-3e61c02ed90b" xlink:href="acmr-20250930.xsd#acmr_LandBuildingsAndPlantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_9a456d86-c6ed-4afc-b26a-1d1942598a1c" xlink:to="loc_acmr_LandBuildingsAndPlantsMember_47efd6a3-3dd8-49b6-9ec0-3e61c02ed90b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_5d62d12e-7311-4591-a0cc-f565cdea58c0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_2a3ee6a3-c319-4fc8-857d-4c15675e568f" xlink:to="loc_srt_RangeAxis_5d62d12e-7311-4591-a0cc-f565cdea58c0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5d62d12e-7311-4591-a0cc-f565cdea58c0_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_5d62d12e-7311-4591-a0cc-f565cdea58c0" xlink:to="loc_srt_RangeMember_5d62d12e-7311-4591-a0cc-f565cdea58c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3da3c95e-e006-48fd-b8cd-71a7c417a2e4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_5d62d12e-7311-4591-a0cc-f565cdea58c0" xlink:to="loc_srt_RangeMember_3da3c95e-e006-48fd-b8cd-71a7c417a2e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_964e042b-8912-4499-9acc-8447765fe9b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c581340f-6bb5-4fa2-852a-4db662144d1b" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_964e042b-8912-4499-9acc-8447765fe9b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_8859b9b4-5e77-4b4d-a338-5ce8acb71c9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c581340f-6bb5-4fa2-852a-4db662144d1b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_8859b9b4-5e77-4b4d-a338-5ce8acb71c9b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/SHORTTERMBORROWINGSShortTermBorrowingsDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#SHORTTERMBORROWINGSShortTermBorrowingsDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/SHORTTERMBORROWINGSShortTermBorrowingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtLineItems_323c67de-28e9-4f10-8d04-43e3ae9e3512" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShortTermDebtTable_9d7e356d-ac5a-464c-825d-d32e48ed2d1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShortTermDebtTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShortTermDebtLineItems_323c67de-28e9-4f10-8d04-43e3ae9e3512" xlink:to="loc_us-gaap_ScheduleOfShortTermDebtTable_9d7e356d-ac5a-464c-825d-d32e48ed2d1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_2f8c80ed-8969-46a9-a5a5-0e2313399f95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_9d7e356d-ac5a-464c-825d-d32e48ed2d1e" xlink:to="loc_us-gaap_DebtInstrumentAxis_2f8c80ed-8969-46a9-a5a5-0e2313399f95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_2f8c80ed-8969-46a9-a5a5-0e2313399f95_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_2f8c80ed-8969-46a9-a5a5-0e2313399f95" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_2f8c80ed-8969-46a9-a5a5-0e2313399f95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6c6211e7-4d1c-49dc-baf4-8f025b90f0fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_2f8c80ed-8969-46a9-a5a5-0e2313399f95" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6c6211e7-4d1c-49dc-baf4-8f025b90f0fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6c6211e7-4d1c-49dc-baf4-8f025b90f0fb" xlink:to="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnFebruary272025WithAnAnnualInterestRateOf2.60Member_5d6ccc88-a038-48b2-b721-5d730ea4207e" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnFebruary272025WithAnAnnualInterestRateOf2.60Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnFebruary272025WithAnAnnualInterestRateOf2.60Member_5d6ccc88-a038-48b2-b721-5d730ea4207e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnFebruary282025WithAnAnnualInterestRateOf2.60Member_adab80fa-3b25-4e82-be48-55e050eb5e42" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnFebruary282025WithAnAnnualInterestRateOf2.60Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnFebruary282025WithAnAnnualInterestRateOf2.60Member_adab80fa-3b25-4e82-be48-55e050eb5e42" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch12025WithAnAnnualInterestRateOf2.60Member_16b712af-4e26-4019-bb38-0acaa3f78dfe" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnMarch12025WithAnAnnualInterestRateOf2.60Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch12025WithAnAnnualInterestRateOf2.60Member_16b712af-4e26-4019-bb38-0acaa3f78dfe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch52025WithAnAnnualInterestRateOf2.60Member_566a2354-342b-4987-8bfe-ffd299f30dbf" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnMarch52025WithAnAnnualInterestRateOf2.60Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch52025WithAnAnnualInterestRateOf2.60Member_566a2354-342b-4987-8bfe-ffd299f30dbf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch82025WithAnAnnualInterestRateOf2.60Member_6799b2a2-ca5d-4992-b96c-2e0d1fdbbe26" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnMarch82025WithAnAnnualInterestRateOf2.60Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch82025WithAnAnnualInterestRateOf2.60Member_6799b2a2-ca5d-4992-b96c-2e0d1fdbbe26" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnAugust272025WithAnAnnualInterestRateOf2.60Member_9162db8c-a2cd-413d-aec8-2bd0923ab46a" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnAugust272025WithAnAnnualInterestRateOf2.60Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnAugust272025WithAnAnnualInterestRateOf2.60Member_9162db8c-a2cd-413d-aec8-2bd0923ab46a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnSeptember122025WithAnAnnualInterestRateOf2.60Member_c6406d0d-6ae6-4d0b-9466-925908d5d6df" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnSeptember122025WithAnAnnualInterestRateOf2.60Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnSeptember122025WithAnAnnualInterestRateOf2.60Member_c6406d0d-6ae6-4d0b-9466-925908d5d6df" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.281Member_76900b1f-320f-480b-abab-3b98757d663c" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.281Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.281Member_76900b1f-320f-480b-abab-3b98757d663c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.282Member_a1c8b66a-89b1-4d8c-9600-74763555df35" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.282Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.282Member_a1c8b66a-89b1-4d8c-9600-74763555df35" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.283Member_143a89cd-3adc-42d5-b328-8e2516b91a01" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.283Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB200000FromChinaMerchantsBankMember_429098f6-1970-4693-b1de-c5f0eb1f5908" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.283Member_143a89cd-3adc-42d5-b328-8e2516b91a01" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditUpToRMB40000FromBankOfChinaMember_adbea24f-230d-4724-9b0a-9b001b0cba89" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditUpToRMB40000FromBankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6c6211e7-4d1c-49dc-baf4-8f025b90f0fb" xlink:to="loc_acmr_LineOfCreditUpToRMB40000FromBankOfChinaMember_adbea24f-230d-4724-9b0a-9b001b0cba89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditDueOnMarch202025WithAnAnnualInterestRateOf2.75.Member_9985eabc-456e-4b18-87f1-ee82a94ea16a" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditDueOnMarch202025WithAnAnnualInterestRateOf2.75.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB40000FromBankOfChinaMember_adbea24f-230d-4724-9b0a-9b001b0cba89" xlink:to="loc_acmr_LineOfCreditDueOnMarch202025WithAnAnnualInterestRateOf2.75.Member_9985eabc-456e-4b18-87f1-ee82a94ea16a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditDueOnSeptember222025WithAnAnnualInterestRateOf2.5.Member_3493c8ed-2f71-40b0-b033-60aba8ccd949" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditDueOnSeptember222025WithAnAnnualInterestRateOf2.5.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB40000FromBankOfChinaMember_adbea24f-230d-4724-9b0a-9b001b0cba89" xlink:to="loc_acmr_LineOfCreditDueOnSeptember222025WithAnAnnualInterestRateOf2.5.Member_3493c8ed-2f71-40b0-b033-60aba8ccd949" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditDueOnApril14th2026WithAnAnnualInterestRateOf2.3Member_a1f28b6a-17c0-4fa4-a66b-b24dfede8fea" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditDueOnApril14th2026WithAnAnnualInterestRateOf2.3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB40000FromBankOfChinaMember_adbea24f-230d-4724-9b0a-9b001b0cba89" xlink:to="loc_acmr_LineOfCreditDueOnApril14th2026WithAnAnnualInterestRateOf2.3Member_a1f28b6a-17c0-4fa4-a66b-b24dfede8fea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditUpToRMB100000FromCiticBankMember_eec6af3d-0210-4e72-9c6a-0b9d2f99eaf0" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditUpToRMB100000FromCiticBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6c6211e7-4d1c-49dc-baf4-8f025b90f0fb" xlink:to="loc_acmr_LineOfCreditUpToRMB100000FromCiticBankMember_eec6af3d-0210-4e72-9c6a-0b9d2f99eaf0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditDueOnJune30th2026WithAnAnnualInterestRateOf2.11Member_07664630-40c1-411e-9718-12f1af95c818" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditDueOnJune30th2026WithAnAnnualInterestRateOf2.11Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToRMB100000FromCiticBankMember_eec6af3d-0210-4e72-9c6a-0b9d2f99eaf0" xlink:to="loc_acmr_LineOfCreditDueOnJune30th2026WithAnAnnualInterestRateOf2.11Member_07664630-40c1-411e-9718-12f1af95c818" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditUpToKRW2000000FromIndustrialBankOfKoreaMember_92093e3a-6a0e-415a-bd12-aa04b23d7b43" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditUpToKRW2000000FromIndustrialBankOfKoreaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6c6211e7-4d1c-49dc-baf4-8f025b90f0fb" xlink:to="loc_acmr_LineOfCreditUpToKRW2000000FromIndustrialBankOfKoreaMember_92093e3a-6a0e-415a-bd12-aa04b23d7b43" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditDueOnDecember162025WithAnAnnualInterestRateOf4.43Member_12c81054-7dd8-4a3b-a985-1f8de3f0af89" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditDueOnDecember162025WithAnAnnualInterestRateOf4.43Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LineOfCreditUpToKRW2000000FromIndustrialBankOfKoreaMember_92093e3a-6a0e-415a-bd12-aa04b23d7b43" xlink:to="loc_acmr_LineOfCreditDueOnDecember162025WithAnAnnualInterestRateOf4.43Member_12c81054-7dd8-4a3b-a985-1f8de3f0af89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_af4c76a6-8b37-481b-80e2-b46b4600f181" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_9d7e356d-ac5a-464c-825d-d32e48ed2d1e" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_af4c76a6-8b37-481b-80e2-b46b4600f181" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_af4c76a6-8b37-481b-80e2-b46b4600f181_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_af4c76a6-8b37-481b-80e2-b46b4600f181" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_af4c76a6-8b37-481b-80e2-b46b4600f181_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_ca8145c3-6f69-41c2-aee5-95fba48469ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_af4c76a6-8b37-481b-80e2-b46b4600f181" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_ca8145c3-6f69-41c2-aee5-95fba48469ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_BankOfChinaMember_7d0fcd12-7fca-42ce-8e89-1833ad72f204" xlink:href="acmr-20250930.xsd#acmr_BankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_ca8145c3-6f69-41c2-aee5-95fba48469ce" xlink:to="loc_acmr_BankOfChinaMember_7d0fcd12-7fca-42ce-8e89-1833ad72f204" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowingsAbstract_98575608-9c4b-44f3-802d-1f329f6e1989" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_323c67de-28e9-4f10-8d04-43e3ae9e3512" xlink:to="loc_us-gaap_ShortTermBorrowingsAbstract_98575608-9c4b-44f3-802d-1f329f6e1989" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_b62bec83-e8e7-4bf4-b3cf-b1219bd79fda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermBorrowingsAbstract_98575608-9c4b-44f3-802d-1f329f6e1989" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_b62bec83-e8e7-4bf4-b3cf-b1219bd79fda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_dc90461c-b320-4757-9afd-01f87901f78e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermBorrowingsAbstract_98575608-9c4b-44f3-802d-1f329f6e1989" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_dc90461c-b320-4757-9afd-01f87901f78e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_ca85b36d-c864-47a2-9731-039054e908e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermBorrowingsAbstract_98575608-9c4b-44f3-802d-1f329f6e1989" xlink:to="loc_us-gaap_ShortTermBorrowings_ca85b36d-c864-47a2-9731-039054e908e8" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/SHORTTERMBORROWINGSNarrativeDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#SHORTTERMBORROWINGSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/SHORTTERMBORROWINGSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtLineItems_936abe05-bb3f-48b5-b19b-560c1b59ea24" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShortTermDebtTable_9cdb169d-9622-436a-81e3-9da1599609a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShortTermDebtTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShortTermDebtLineItems_936abe05-bb3f-48b5-b19b-560c1b59ea24" xlink:to="loc_us-gaap_ScheduleOfShortTermDebtTable_9cdb169d-9622-436a-81e3-9da1599609a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_84784273-7c6c-4f80-b5eb-c90931e08f3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_9cdb169d-9622-436a-81e3-9da1599609a3" xlink:to="loc_us-gaap_DebtInstrumentAxis_84784273-7c6c-4f80-b5eb-c90931e08f3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_84784273-7c6c-4f80-b5eb-c90931e08f3d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_84784273-7c6c-4f80-b5eb-c90931e08f3d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_84784273-7c6c-4f80-b5eb-c90931e08f3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_46f03c6d-1cad-4c35-8ec6-a0e9c2985c7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_84784273-7c6c-4f80-b5eb-c90931e08f3d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_46f03c6d-1cad-4c35-8ec6-a0e9c2985c7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.283Member_a9b2726e-1d74-4940-a673-1bcda1637d47" xlink:href="acmr-20250930.xsd#acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.283Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_46f03c6d-1cad-4c35-8ec6-a0e9c2985c7e" xlink:to="loc_acmr_LineOfCreditChinaMerchantsBankDueOnMarch122026WithAnAnnualInterestRateOf2.283Member_a9b2726e-1d74-4940-a673-1bcda1637d47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_360a691f-f4e0-4ba3-b8bc-a8cab8da4137" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_936abe05-bb3f-48b5-b19b-560c1b59ea24" xlink:to="loc_us-gaap_ShortTermBorrowings_360a691f-f4e0-4ba3-b8bc-a8cab8da4137" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/LONGTERMBORROWINGSSummaryofLongtermBorrowingsDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#LONGTERMBORROWINGSSummaryofLongtermBorrowingsDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/LONGTERMBORROWINGSSummaryofLongtermBorrowingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_a7af7047-f596-4c88-9619-444b5d04016a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_6e771944-fc22-40cf-8f4d-fe83e498cccc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_a7af7047-f596-4c88-9619-444b5d04016a" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_6e771944-fc22-40cf-8f4d-fe83e498cccc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_e1740ee0-4b21-47d6-a569-91e8a2ae8135" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_6e771944-fc22-40cf-8f4d-fe83e498cccc" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_e1740ee0-4b21-47d6-a569-91e8a2ae8135" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_e1740ee0-4b21-47d6-a569-91e8a2ae8135_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_e1740ee0-4b21-47d6-a569-91e8a2ae8135" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_e1740ee0-4b21-47d6-a569-91e8a2ae8135_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_e1740ee0-4b21-47d6-a569-91e8a2ae8135" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ChinaMerchantsBankMember_e1da270b-b29b-4301-9bae-e9dfc0edb887" xlink:href="acmr-20250930.xsd#acmr_ChinaMerchantsBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:to="loc_acmr_ChinaMerchantsBankMember_e1da270b-b29b-4301-9bae-e9dfc0edb887" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_AgriculturalBankOfChinaMember_137e1341-54d9-4a2c-9367-4372e683431d" xlink:href="acmr-20250930.xsd#acmr_AgriculturalBankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:to="loc_acmr_AgriculturalBankOfChinaMember_137e1341-54d9-4a2c-9367-4372e683431d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_BankOfChinaMember_b9bd7ab7-65b5-4c1b-93f9-d44dec3c3c3d" xlink:href="acmr-20250930.xsd#acmr_BankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:to="loc_acmr_BankOfChinaMember_b9bd7ab7-65b5-4c1b-93f9-d44dec3c3c3d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_BankOfShanghaiMember_53a62c25-6573-4e4a-88dd-4b97b71e6ea8" xlink:href="acmr-20250930.xsd#acmr_BankOfShanghaiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:to="loc_acmr_BankOfShanghaiMember_53a62c25-6573-4e4a-88dd-4b97b71e6ea8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CITICBankMember_2a8a7368-1da9-401e-bca9-64f7431a01d6" xlink:href="acmr-20250930.xsd#acmr_CITICBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:to="loc_acmr_CITICBankMember_2a8a7368-1da9-401e-bca9-64f7431a01d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_EverbrightBankMember_14367f53-87aa-45c2-be28-25ae60229c35" xlink:href="acmr-20250930.xsd#acmr_EverbrightBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:to="loc_acmr_EverbrightBankMember_14367f53-87aa-45c2-be28-25ae60229c35" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_IndustrialAndCommercialBankOfChinaMember_03e76f61-47df-42ba-a1f7-873282aec380" xlink:href="acmr-20250930.xsd#acmr_IndustrialAndCommercialBankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_a82b7a5b-1d08-4f58-a006-4823c4863526" xlink:to="loc_acmr_IndustrialAndCommercialBankOfChinaMember_03e76f61-47df-42ba-a1f7-873282aec380" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_cd662678-1da2-4743-a1ce-36408f011a63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtCurrentAndNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_a7af7047-f596-4c88-9619-444b5d04016a" xlink:to="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_cd662678-1da2-4743-a1ce-36408f011a63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_dfcc804f-3355-46ca-8f8c-39c11bee2ecb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_cd662678-1da2-4743-a1ce-36408f011a63" xlink:to="loc_us-gaap_LongTermDebt_dfcc804f-3355-46ca-8f8c-39c11bee2ecb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_2f094e84-6fc4-4cfa-93c7-3a41507fe800" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_cd662678-1da2-4743-a1ce-36408f011a63" xlink:to="loc_us-gaap_LongTermDebtCurrent_2f094e84-6fc4-4cfa-93c7-3a41507fe800" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_96b79364-6e51-4f84-9637-76c732512d66" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtCurrentAndNoncurrentAbstract_cd662678-1da2-4743-a1ce-36408f011a63" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_96b79364-6e51-4f84-9637-76c732512d66" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/LONGTERMBORROWINGSNarrativeDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#LONGTERMBORROWINGSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/LONGTERMBORROWINGSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_25eaa1e0-fdf8-41d7-aa9c-53808c438ca1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_25eaa1e0-fdf8-41d7-aa9c-53808c438ca1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_20a083e3-b1d9-42ba-9b18-e4d49a89c174" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_25eaa1e0-fdf8-41d7-aa9c-53808c438ca1" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_20a083e3-b1d9-42ba-9b18-e4d49a89c174" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_20a083e3-b1d9-42ba-9b18-e4d49a89c174_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_20a083e3-b1d9-42ba-9b18-e4d49a89c174" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_20a083e3-b1d9-42ba-9b18-e4d49a89c174_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_c7b23ffa-31f1-4e86-b683-2c2b2ddc8637" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_20a083e3-b1d9-42ba-9b18-e4d49a89c174" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_c7b23ffa-31f1-4e86-b683-2c2b2ddc8637" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_BankOfChinaMember_7703f2bf-04c6-4678-84f3-f1e4fc5e8a52" xlink:href="acmr-20250930.xsd#acmr_BankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_c7b23ffa-31f1-4e86-b683-2c2b2ddc8637" xlink:to="loc_acmr_BankOfChinaMember_7703f2bf-04c6-4678-84f3-f1e4fc5e8a52" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CITICBankMember_8308b6f1-2b08-485f-97a5-e1d3f4a787c8" xlink:href="acmr-20250930.xsd#acmr_CITICBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_c7b23ffa-31f1-4e86-b683-2c2b2ddc8637" xlink:to="loc_acmr_CITICBankMember_8308b6f1-2b08-485f-97a5-e1d3f4a787c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_IndustrialAndCommercialBankOfChinaMember_cd0737eb-b91a-47de-b382-f0df9c676f56" xlink:href="acmr-20250930.xsd#acmr_IndustrialAndCommercialBankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_c7b23ffa-31f1-4e86-b683-2c2b2ddc8637" xlink:to="loc_acmr_IndustrialAndCommercialBankOfChinaMember_cd0737eb-b91a-47de-b382-f0df9c676f56" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ChinaMerchantsBankMember_2fb60b07-259d-4f47-a653-0c9504463d44" xlink:href="acmr-20250930.xsd#acmr_ChinaMerchantsBankMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_c7b23ffa-31f1-4e86-b683-2c2b2ddc8637" xlink:to="loc_acmr_ChinaMerchantsBankMember_2fb60b07-259d-4f47-a653-0c9504463d44" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_AgriculturalBankOfChinaMember_0462ac26-7296-454c-b459-d0400be9232e" xlink:href="acmr-20250930.xsd#acmr_AgriculturalBankOfChinaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_c7b23ffa-31f1-4e86-b683-2c2b2ddc8637" xlink:to="loc_acmr_AgriculturalBankOfChinaMember_0462ac26-7296-454c-b459-d0400be9232e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_79239886-b4ae-4be5-8f50-9eb21284a7d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_25eaa1e0-fdf8-41d7-aa9c-53808c438ca1" xlink:to="loc_us-gaap_DebtInstrumentAxis_79239886-b4ae-4be5-8f50-9eb21284a7d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_79239886-b4ae-4be5-8f50-9eb21284a7d3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_79239886-b4ae-4be5-8f50-9eb21284a7d3" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_79239886-b4ae-4be5-8f50-9eb21284a7d3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_559ff1eb-85e1-44a9-a978-a39c2f9bd806" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_79239886-b4ae-4be5-8f50-9eb21284a7d3" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_559ff1eb-85e1-44a9-a978-a39c2f9bd806" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_BankOfChinaJune2025FacilityMember_1ae1de38-11c9-4ee6-a5b6-a03f362964fc" xlink:href="acmr-20250930.xsd#acmr_BankOfChinaJune2025FacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_559ff1eb-85e1-44a9-a978-a39c2f9bd806" xlink:to="loc_acmr_BankOfChinaJune2025FacilityMember_1ae1de38-11c9-4ee6-a5b6-a03f362964fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_d828471c-c181-4856-85eb-ee9d20b02856" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_d828471c-c181-4856-85eb-ee9d20b02856" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_NumberOfInstallmentsForLoanRepayable_0680c2ad-1eb0-437f-8b45-e2950d0f9e29" xlink:href="acmr-20250930.xsd#acmr_NumberOfInstallmentsForLoanRepayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_acmr_NumberOfInstallmentsForLoanRepayable_0680c2ad-1eb0-437f-8b45-e2950d0f9e29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_5d55abc3-ebdc-4096-9772-3792edb12596" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_5d55abc3-ebdc-4096-9772-3792edb12596" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_DebtInstrumentCovenantPercentageOfPrincipalAmountRepaid_c0ab0dcb-fff6-4f0b-b87e-cc2633ad65e1" xlink:href="acmr-20250930.xsd#acmr_DebtInstrumentCovenantPercentageOfPrincipalAmountRepaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_acmr_DebtInstrumentCovenantPercentageOfPrincipalAmountRepaid_c0ab0dcb-fff6-4f0b-b87e-cc2633ad65e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_DebtInstrumentCovenantPrincipalRepaymentPeriod_50b534be-4dc5-4519-9d67-677540e026d6" xlink:href="acmr-20250930.xsd#acmr_DebtInstrumentCovenantPrincipalRepaymentPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_acmr_DebtInstrumentCovenantPrincipalRepaymentPeriod_50b534be-4dc5-4519-9d67-677540e026d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_DebtInstrumentCovenantPrincipalPaymentRevisionPeriod_a5e0818f-43b3-4e7d-b8b3-7213fa88344a" xlink:href="acmr-20250930.xsd#acmr_DebtInstrumentCovenantPrincipalPaymentRevisionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_acmr_DebtInstrumentCovenantPrincipalPaymentRevisionPeriod_a5e0818f-43b3-4e7d-b8b3-7213fa88344a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_DebtInstrumentCovenantProceedsFromOfferingThreshold_f142bb0f-d655-4030-a091-b0b3dc44d58a" xlink:href="acmr-20250930.xsd#acmr_DebtInstrumentCovenantProceedsFromOfferingThreshold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_acmr_DebtInstrumentCovenantProceedsFromOfferingThreshold_f142bb0f-d655-4030-a091-b0b3dc44d58a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_37300784-8c91-4727-b7b7-73d40ab58840" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7d9b73df-097b-44e0-9ff9-47fefd22bdda" xlink:to="loc_us-gaap_LongTermDebtFairValue_37300784-8c91-4727-b7b7-73d40ab58840" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/LONGTERMINVESTMENTSNarrativeDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#LONGTERMINVESTMENTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/LONGTERMINVESTMENTSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LongTermInvestmentLineItems_b5f577fa-6b18-4d8d-8664-852cd8d656bc" xlink:href="acmr-20250930.xsd#acmr_LongTermInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LongTermInvestmentsTable_bfddf3f9-d7d5-477b-9530-624b4d29ee8d" xlink:href="acmr-20250930.xsd#acmr_LongTermInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_acmr_LongTermInvestmentLineItems_b5f577fa-6b18-4d8d-8664-852cd8d656bc" xlink:to="loc_acmr_LongTermInvestmentsTable_bfddf3f9-d7d5-477b-9530-624b4d29ee8d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_f6751fc3-8082-426e-87d9-da508b81b15f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_acmr_LongTermInvestmentsTable_bfddf3f9-d7d5-477b-9530-624b4d29ee8d" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_f6751fc3-8082-426e-87d9-da508b81b15f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_f6751fc3-8082-426e-87d9-da508b81b15f_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_f6751fc3-8082-426e-87d9-da508b81b15f" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_f6751fc3-8082-426e-87d9-da508b81b15f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_1c6781ec-ef96-425e-95b7-ad0231d25280" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_f6751fc3-8082-426e-87d9-da508b81b15f" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_1c6781ec-ef96-425e-95b7-ad0231d25280" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_NinebellACMShanghaiMember_c501c457-f2aa-4273-936a-54f828882c43" xlink:href="acmr-20250930.xsd#acmr_NinebellACMShanghaiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_1c6781ec-ef96-425e-95b7-ad0231d25280" xlink:to="loc_acmr_NinebellACMShanghaiMember_c501c457-f2aa-4273-936a-54f828882c43" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsAbstract_53d02b49-866d-4e30-845a-268034d5a8e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LongTermInvestmentLineItems_b5f577fa-6b18-4d8d-8664-852cd8d656bc" xlink:to="loc_us-gaap_InvestmentsAbstract_53d02b49-866d-4e30-845a-268034d5a8e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_750f95fd-d7e9-49bc-a835-89b2b323ec0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAbstract_53d02b49-866d-4e30-845a-268034d5a8e9" xlink:to="loc_us-gaap_EquityMethodInvestments_750f95fd-d7e9-49bc-a835-89b2b323ec0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_19616bee-16f5-41dc-ac04-bd7d0b78fedd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsAbstract_53d02b49-866d-4e30-845a-268034d5a8e9" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_19616bee-16f5-41dc-ac04-bd7d0b78fedd" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/LONGTERMINVESTMENTSSummaryofLongTermInvestmentsDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#LONGTERMINVESTMENTSSummaryofLongTermInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/LONGTERMINVESTMENTSSummaryofLongTermInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LongTermInvestmentsLineItems_e8ce8d98-ccc9-4c2f-b6f1-db438d21e962" xlink:href="acmr-20250930.xsd#acmr_LongTermInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LongTermInvestmentsTable_c9c8503b-a44d-4719-9921-ed6ef3d3a799" xlink:href="acmr-20250930.xsd#acmr_LongTermInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_acmr_LongTermInvestmentsLineItems_e8ce8d98-ccc9-4c2f-b6f1-db438d21e962" xlink:to="loc_acmr_LongTermInvestmentsTable_c9c8503b-a44d-4719-9921-ed6ef3d3a799" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_79bddcc3-925a-416f-af79-485329d887c4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_acmr_LongTermInvestmentsTable_c9c8503b-a44d-4719-9921-ed6ef3d3a799" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_79bddcc3-925a-416f-af79-485329d887c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_79bddcc3-925a-416f-af79-485329d887c4_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_79bddcc3-925a-416f-af79-485329d887c4" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_79bddcc3-925a-416f-af79-485329d887c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_79bddcc3-925a-416f-af79-485329d887c4" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_NinebellCompanyLimitedMember_c397cc03-02ce-4188-80ad-81860a2dc658" xlink:href="acmr-20250930.xsd#acmr_NinebellCompanyLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_NinebellCompanyLimitedMember_c397cc03-02ce-4188-80ad-81860a2dc658" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_NinebellCompanyLimitedACMShanghaiMember_658738b6-ed7a-49e1-8ee5-1539d43c411a" xlink:href="acmr-20250930.xsd#acmr_NinebellCompanyLimitedACMShanghaiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_NinebellCompanyLimitedACMShanghaiMember_658738b6-ed7a-49e1-8ee5-1539d43c411a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_WooilFluconCompanyLimitedMember_c3bd6926-61bf-42c8-9b3a-37712d834f11" xlink:href="acmr-20250930.xsd#acmr_WooilFluconCompanyLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_WooilFluconCompanyLimitedMember_c3bd6926-61bf-42c8-9b3a-37712d834f11" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_HefeiShixiChanhengIntegratedCircuitIndustryVentureCapitalFundPartnershipMember_a7c37527-dd1f-4db3-9821-120cc4626153" xlink:href="acmr-20250930.xsd#acmr_HefeiShixiChanhengIntegratedCircuitIndustryVentureCapitalFundPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_HefeiShixiChanhengIntegratedCircuitIndustryVentureCapitalFundPartnershipMember_a7c37527-dd1f-4db3-9821-120cc4626153" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ShengyiSemiconductorTechnologyCompanyLimitedMember_c3c00664-404f-4916-94ca-415f83cc6b47" xlink:href="acmr-20250930.xsd#acmr_ShengyiSemiconductorTechnologyCompanyLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_ShengyiSemiconductorTechnologyCompanyLimitedMember_c3c00664-404f-4916-94ca-415f83cc6b47" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CompanyDMember_7e78e83d-00c2-41bf-b67a-51bed7f4a656" xlink:href="acmr-20250930.xsd#acmr_CompanyDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_CompanyDMember_7e78e83d-00c2-41bf-b67a-51bed7f4a656" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ShengyiMember_1663a237-0e52-4e98-862a-0e6d69c8c23d" xlink:href="acmr-20250930.xsd#acmr_ShengyiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_ShengyiMember_1663a237-0e52-4e98-862a-0e6d69c8c23d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CompanyAMember_f3dc4655-21fb-4930-8baa-ec96be2f911a" xlink:href="acmr-20250930.xsd#acmr_CompanyAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_CompanyAMember_f3dc4655-21fb-4930-8baa-ec96be2f911a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CompanyBMember_419d521f-17d3-4bd8-99fe-9fbeeea60078" xlink:href="acmr-20250930.xsd#acmr_CompanyBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_CompanyBMember_419d521f-17d3-4bd8-99fe-9fbeeea60078" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CompanyCMember_cf9547cb-6a00-450d-94fd-2ea93dabc076" xlink:href="acmr-20250930.xsd#acmr_CompanyCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_CompanyCMember_cf9547cb-6a00-450d-94fd-2ea93dabc076" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CompanyEMember_1a8cd3ef-2230-46eb-89fc-fabb506afc4c" xlink:href="acmr-20250930.xsd#acmr_CompanyEMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_CompanyEMember_1a8cd3ef-2230-46eb-89fc-fabb506afc4c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CompanyFMember_3c1ec154-07bd-4478-8dec-34cb3875f1ab" xlink:href="acmr-20250930.xsd#acmr_CompanyFMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_CompanyFMember_3c1ec154-07bd-4478-8dec-34cb3875f1ab" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_CompanyGMember_75714831-cc54-4fa3-afe8-94dc8c5c0e29" xlink:href="acmr-20250930.xsd#acmr_CompanyGMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_CompanyGMember_75714831-cc54-4fa3-afe8-94dc8c5c0e29" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_OtherMember_2a2ba9c8-2b53-48a8-afad-188c713feca1" xlink:href="acmr-20250930.xsd#acmr_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_OtherMember_2a2ba9c8-2b53-48a8-afad-188c713feca1" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_SubtotalMeasurementAlternativeMember_e5785d3b-759f-4ee6-9fe2-e75bda98f774" xlink:href="acmr-20250930.xsd#acmr_SubtotalMeasurementAlternativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_21186598-c92d-42c3-a622-13db56184108" xlink:to="loc_acmr_SubtotalMeasurementAlternativeMember_e5785d3b-759f-4ee6-9fe2-e75bda98f774" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_3b02986b-90d5-4e82-a9a6-61cb23ed1e6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_acmr_LongTermInvestmentsTable_c9c8503b-a44d-4719-9921-ed6ef3d3a799" xlink:to="loc_us-gaap_StatementClassOfStockAxis_3b02986b-90d5-4e82-a9a6-61cb23ed1e6e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_3b02986b-90d5-4e82-a9a6-61cb23ed1e6e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3b02986b-90d5-4e82-a9a6-61cb23ed1e6e" xlink:to="loc_us-gaap_ClassOfStockDomain_3b02986b-90d5-4e82-a9a6-61cb23ed1e6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_c260c72a-1511-40a4-9b85-16a333b3c607" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3b02986b-90d5-4e82-a9a6-61cb23ed1e6e" xlink:to="loc_us-gaap_ClassOfStockDomain_c260c72a-1511-40a4-9b85-16a333b3c607" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_40b7dc82-4c16-403b-b628-3243a4c6239b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_c260c72a-1511-40a4-9b85-16a333b3c607" xlink:to="loc_us-gaap_CommonClassAMember_40b7dc82-4c16-403b-b628-3243a4c6239b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_8995de5a-61ab-442d-9d41-01ff7db16d54" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_acmr_LongTermInvestmentsTable_c9c8503b-a44d-4719-9921-ed6ef3d3a799" xlink:to="loc_us-gaap_InvestmentTypeAxis_8995de5a-61ab-442d-9d41-01ff7db16d54" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_8995de5a-61ab-442d-9d41-01ff7db16d54_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_8995de5a-61ab-442d-9d41-01ff7db16d54" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_8995de5a-61ab-442d-9d41-01ff7db16d54_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_f68c5dee-797c-4306-92de-4f665a674e63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_8995de5a-61ab-442d-9d41-01ff7db16d54" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_f68c5dee-797c-4306-92de-4f665a674e63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_InvestmentExcludingOtherMember_7e90fec1-c8e0-46fb-8301-723c1f21e3fd" xlink:href="acmr-20250930.xsd#acmr_InvestmentExcludingOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_f68c5dee-797c-4306-92de-4f665a674e63" xlink:to="loc_acmr_InvestmentExcludingOtherMember_7e90fec1-c8e0-46fb-8301-723c1f21e3fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_aa998a35-bac2-46ad-a48e-e49e46360cfd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_f68c5dee-797c-4306-92de-4f665a674e63" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_aa998a35-bac2-46ad-a48e-e49e46360cfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableforsaleSecuritiesMember_0acd3990-b412-4c78-9555-49f5ea78441c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableforsaleSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_f68c5dee-797c-4306-92de-4f665a674e63" xlink:to="loc_us-gaap_AvailableforsaleSecuritiesMember_0acd3990-b412-4c78-9555-49f5ea78441c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_7a1ac458-fbc9-48fd-a854-df29b2ebfd9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LongTermInvestmentsLineItems_e8ce8d98-ccc9-4c2f-b6f1-db438d21e962" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_7a1ac458-fbc9-48fd-a854-df29b2ebfd9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_2a2f61ae-251d-4aec-8c0a-bd6324128b32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LongTermInvestmentsLineItems_e8ce8d98-ccc9-4c2f-b6f1-db438d21e962" xlink:to="loc_us-gaap_EquityMethodInvestments_2a2f61ae-251d-4aec-8c0a-bd6324128b32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermInvestments_a8edc148-01bb-4165-a432-a76de41e35b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_LongTermInvestmentsLineItems_e8ce8d98-ccc9-4c2f-b6f1-db438d21e962" xlink:to="loc_us-gaap_LongTermInvestments_a8edc148-01bb-4165-a432-a76de41e35b7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/RELATEDPARTYBALANCESANDTRANSACTIONSDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#RELATEDPARTYBALANCESANDTRANSACTIONSDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/RELATEDPARTYBALANCESANDTRANSACTIONSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_284a6b3a-12fa-4f70-9245-c6566e040895" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_0412af60-9790-46f8-b15e-ef56fe0a5de5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_284a6b3a-12fa-4f70-9245-c6566e040895" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_0412af60-9790-46f8-b15e-ef56fe0a5de5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0315118b-8024-4fbd-b87b-c5dafe02c1bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_0412af60-9790-46f8-b15e-ef56fe0a5de5" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0315118b-8024-4fbd-b87b-c5dafe02c1bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_0315118b-8024-4fbd-b87b-c5dafe02c1bc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0315118b-8024-4fbd-b87b-c5dafe02c1bc" xlink:to="loc_us-gaap_RelatedPartyDomain_0315118b-8024-4fbd-b87b-c5dafe02c1bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_d59a9003-7741-4ce6-800a-2ee95520c558" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0315118b-8024-4fbd-b87b-c5dafe02c1bc" xlink:to="loc_us-gaap_RelatedPartyDomain_d59a9003-7741-4ce6-800a-2ee95520c558" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_8a085e69-6433-4799-985d-a9e61562b19b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_d59a9003-7741-4ce6-800a-2ee95520c558" xlink:to="loc_us-gaap_RelatedPartyMember_8a085e69-6433-4799-985d-a9e61562b19b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_8bce49ef-276b-434c-bd94-43736d6628e9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_0412af60-9790-46f8-b15e-ef56fe0a5de5" xlink:to="loc_srt_CounterpartyNameAxis_8bce49ef-276b-434c-bd94-43736d6628e9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_8bce49ef-276b-434c-bd94-43736d6628e9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_8bce49ef-276b-434c-bd94-43736d6628e9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_8bce49ef-276b-434c-bd94-43736d6628e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cab3bb01-8d4a-413d-89d0-04635137252a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_8bce49ef-276b-434c-bd94-43736d6628e9" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cab3bb01-8d4a-413d-89d0-04635137252a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_NinebellCoLtdMember_63ba62db-8903-4190-bb4b-77906786b221" xlink:href="acmr-20250930.xsd#acmr_NinebellCoLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cab3bb01-8d4a-413d-89d0-04635137252a" xlink:to="loc_acmr_NinebellCoLtdMember_63ba62db-8903-4190-bb4b-77906786b221" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ShengyiSemiconductorTechnologyCoLtdMember_b524c0ff-c293-4043-88cb-574cd91cbcc7" xlink:href="acmr-20250930.xsd#acmr_ShengyiSemiconductorTechnologyCoLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_cab3bb01-8d4a-413d-89d0-04635137252a" xlink:to="loc_acmr_ShengyiSemiconductorTechnologyCoLtdMember_b524c0ff-c293-4043-88cb-574cd91cbcc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivablesNetCurrent_20e93902-2ca6-4c05-a8d0-cfbd7e514ac4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_284a6b3a-12fa-4f70-9245-c6566e040895" xlink:to="loc_us-gaap_OtherReceivablesNetCurrent_20e93902-2ca6-4c05-a8d0-cfbd7e514ac4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_10c06549-cc48-4237-8a6f-58d64e54bd39" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_284a6b3a-12fa-4f70-9245-c6566e040895" xlink:to="loc_us-gaap_AccountsPayableCurrent_10c06549-cc48-4237-8a6f-58d64e54bd39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty_26e54ecd-e33a-4518-87fd-5d38fb9c553b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_284a6b3a-12fa-4f70-9245-c6566e040895" xlink:to="loc_us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty_26e54ecd-e33a-4518-87fd-5d38fb9c553b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_0efb3b6e-c6f1-4ac5-90ac-ab3f3d5177d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_284a6b3a-12fa-4f70-9245-c6566e040895" xlink:to="loc_us-gaap_CostOfRevenue_0efb3b6e-c6f1-4ac5-90ac-ab3f3d5177d3" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/COMMONSTOCKDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#COMMONSTOCKDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/COMMONSTOCKDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_b4417167-2ba8-446f-8e16-cbf8d66ca1ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_b4417167-2ba8-446f-8e16-cbf8d66ca1ba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_022d44f8-f7e6-413c-91f1-b0d2f816f67e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_b4417167-2ba8-446f-8e16-cbf8d66ca1ba" xlink:to="loc_us-gaap_StatementClassOfStockAxis_022d44f8-f7e6-413c-91f1-b0d2f816f67e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_022d44f8-f7e6-413c-91f1-b0d2f816f67e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_022d44f8-f7e6-413c-91f1-b0d2f816f67e" xlink:to="loc_us-gaap_ClassOfStockDomain_022d44f8-f7e6-413c-91f1-b0d2f816f67e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_52323651-96cf-4622-a44d-7efbab214ca6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_022d44f8-f7e6-413c-91f1-b0d2f816f67e" xlink:to="loc_us-gaap_ClassOfStockDomain_52323651-96cf-4622-a44d-7efbab214ca6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_4634f802-da31-4052-8d04-2480db853584" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_52323651-96cf-4622-a44d-7efbab214ca6" xlink:to="loc_us-gaap_CommonClassAMember_4634f802-da31-4052-8d04-2480db853584" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_5ab189ed-0efc-474f-90a1-d3265e088267" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_52323651-96cf-4622-a44d-7efbab214ca6" xlink:to="loc_us-gaap_CommonClassBMember_5ab189ed-0efc-474f-90a1-d3265e088267" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_133aa929-7932-4bf8-ab40-653d654261a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_133aa929-7932-4bf8-ab40-653d654261a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_7e644c72-adb0-404d-8fba-b51513e08d0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_7e644c72-adb0-404d-8fba-b51513e08d0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_VotingRightsPerShare_c20a2630-ef52-46f3-ad82-ca956386daaa" xlink:href="acmr-20250930.xsd#acmr_VotingRightsPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:to="loc_acmr_VotingRightsPerShare_c20a2630-ef52-46f3-ad82-ca956386daaa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConversionOfStockSharesConverted1_75a31e67-3880-4f86-9fea-0a814520b856" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConversionOfStockSharesConverted1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:to="loc_us-gaap_ConversionOfStockSharesConverted1_75a31e67-3880-4f86-9fea-0a814520b856" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_2ef22e17-3fb2-4f79-9abd-82a973595af7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:to="loc_us-gaap_CommonStockSharesIssued_2ef22e17-3fb2-4f79-9abd-82a973595af7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_60fecab6-bdd3-469d-818a-d9607ec3be57" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2160873e-ef7f-47c8-81c3-51b36c26b978" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_60fecab6-bdd3-469d-818a-d9607ec3be57" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/STOCKBASEDCOMPENSATIONNarrativeDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#STOCKBASEDCOMPENSATIONNarrativeDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/STOCKBASEDCOMPENSATIONNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_43a8f42e-b601-4356-9d5a-73497cde863c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_cd1609d1-7c73-4350-876b-7d64bf921be5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_43a8f42e-b601-4356-9d5a-73497cde863c" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_cd1609d1-7c73-4350-876b-7d64bf921be5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_e5e2c01f-c9e3-43be-9422-98db5d939fbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_cd1609d1-7c73-4350-876b-7d64bf921be5" xlink:to="loc_us-gaap_AwardTypeAxis_e5e2c01f-c9e3-43be-9422-98db5d939fbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e5e2c01f-c9e3-43be-9422-98db5d939fbf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_e5e2c01f-c9e3-43be-9422-98db5d939fbf" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e5e2c01f-c9e3-43be-9422-98db5d939fbf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_414d0369-01eb-4b33-90f9-7ee3837efdd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_e5e2c01f-c9e3-43be-9422-98db5d939fbf" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_414d0369-01eb-4b33-90f9-7ee3837efdd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_4bc6c6b6-391a-4c90-9e23-96d7b9be8216" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_414d0369-01eb-4b33-90f9-7ee3837efdd5" xlink:to="loc_us-gaap_EmployeeStockOptionMember_4bc6c6b6-391a-4c90-9e23-96d7b9be8216" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusAxis_43c294f0-8fdd-48b2-81e1-111a9ceffdb3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_cd1609d1-7c73-4350-876b-7d64bf921be5" xlink:to="loc_us-gaap_GranteeStatusAxis_43c294f0-8fdd-48b2-81e1-111a9ceffdb3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_43c294f0-8fdd-48b2-81e1-111a9ceffdb3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GranteeStatusAxis_43c294f0-8fdd-48b2-81e1-111a9ceffdb3" xlink:to="loc_us-gaap_GranteeStatusDomain_43c294f0-8fdd-48b2-81e1-111a9ceffdb3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_5a55a593-5ab1-4dd2-b9a0-362da53118ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GranteeStatusAxis_43c294f0-8fdd-48b2-81e1-111a9ceffdb3" xlink:to="loc_us-gaap_GranteeStatusDomain_5a55a593-5ab1-4dd2-b9a0-362da53118ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_67e9cb9b-a5c9-454c-9ca2-117b50d2d494" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedPaymentArrangementEmployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_5a55a593-5ab1-4dd2-b9a0-362da53118ae" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_67e9cb9b-a5c9-454c-9ca2-117b50d2d494" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementNonemployeeMember_cacf03cf-63bd-41b5-a797-af6799dd8c78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedPaymentArrangementNonemployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_5a55a593-5ab1-4dd2-b9a0-362da53118ae" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementNonemployeeMember_cacf03cf-63bd-41b5-a797-af6799dd8c78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_ddc10dfd-82c1-4485-a6ac-9b3812a3688a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_43a8f42e-b601-4356-9d5a-73497cde863c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_ddc10dfd-82c1-4485-a6ac-9b3812a3688a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_420e3481-7e8d-4041-8b93-0f2ae02cf040" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_43a8f42e-b601-4356-9d5a-73497cde863c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_420e3481-7e8d-4041-8b93-0f2ae02cf040" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/STOCKBASEDCOMPENSATIONAssumptionsUsedtoDetermineFairValueofShareOptionsGrantedDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#STOCKBASEDCOMPENSATIONAssumptionsUsedtoDetermineFairValueofShareOptionsGrantedDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/STOCKBASEDCOMPENSATIONAssumptionsUsedtoDetermineFairValueofShareOptionsGrantedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d05c676e-5ddd-40bb-9ff8-ae4393c02c2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_13c86e02-40ed-4bbc-b16f-c4b5be23f7ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d05c676e-5ddd-40bb-9ff8-ae4393c02c2f" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_13c86e02-40ed-4bbc-b16f-c4b5be23f7ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_72879fb7-54ea-4a45-977b-affe88b19def" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_13c86e02-40ed-4bbc-b16f-c4b5be23f7ac" xlink:to="loc_us-gaap_AwardTypeAxis_72879fb7-54ea-4a45-977b-affe88b19def" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_72879fb7-54ea-4a45-977b-affe88b19def_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_72879fb7-54ea-4a45-977b-affe88b19def" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_72879fb7-54ea-4a45-977b-affe88b19def_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f78980b0-9525-464b-888a-bb1683a7d791" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_72879fb7-54ea-4a45-977b-affe88b19def" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f78980b0-9525-464b-888a-bb1683a7d791" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_fd682bdc-a6fa-455e-86e2-8e0361ddd60f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f78980b0-9525-464b-888a-bb1683a7d791" xlink:to="loc_us-gaap_EmployeeStockOptionMember_fd682bdc-a6fa-455e-86e2-8e0361ddd60f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d6bd017e-33a9-4611-a98b-620a69bb8fe4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_13c86e02-40ed-4bbc-b16f-c4b5be23f7ac" xlink:to="loc_srt_RangeAxis_d6bd017e-33a9-4611-a98b-620a69bb8fe4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d6bd017e-33a9-4611-a98b-620a69bb8fe4_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d6bd017e-33a9-4611-a98b-620a69bb8fe4" xlink:to="loc_srt_RangeMember_d6bd017e-33a9-4611-a98b-620a69bb8fe4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ac373862-595c-4f5a-9f3d-1dfb078fbbf9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d6bd017e-33a9-4611-a98b-620a69bb8fe4" xlink:to="loc_srt_RangeMember_ac373862-595c-4f5a-9f3d-1dfb078fbbf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_54526d46-b39d-4115-91d9-5b2f7c7b1f21" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ac373862-595c-4f5a-9f3d-1dfb078fbbf9" xlink:to="loc_srt_MinimumMember_54526d46-b39d-4115-91d9-5b2f7c7b1f21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_41cd3f53-239f-4a28-8a2b-7b32a5930a1e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ac373862-595c-4f5a-9f3d-1dfb078fbbf9" xlink:to="loc_srt_MaximumMember_41cd3f53-239f-4a28-8a2b-7b32a5930a1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_d05c676e-5ddd-40bb-9ff8-ae4393c02c2f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_83117a86-33b2-42e2-be83-9d97475264c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:to="loc_us-gaap_SharePrice_83117a86-33b2-42e2-be83-9d97475264c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_7dcc55d9-1b78-4793-b328-cde56a66b6f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_7dcc55d9-1b78-4793-b328-cde56a66b6f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_3b0e227a-9b49-4dc8-9c5e-d65224fb18ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_3b0e227a-9b49-4dc8-9c5e-d65224fb18ed" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_e5622945-3479-4162-8b4e-53e2b49e9d52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_e5622945-3479-4162-8b4e-53e2b49e9d52" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_38078dcf-5c3c-4bd8-b7f4-35047b7d7c25" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_38078dcf-5c3c-4bd8-b7f4-35047b7d7c25" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_b4da0836-751a-40f7-a62e-849d5c538c88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_b4da0836-751a-40f7-a62e-849d5c538c88" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_eda46fd6-d87b-4b51-8541-02ea1edab991" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_725b5210-4869-4ff3-b97d-6fd843d929d5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_eda46fd6-d87b-4b51-8541-02ea1edab991" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/STOCKBASEDCOMPENSATIONStockbasedCompensationExpenseDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#STOCKBASEDCOMPENSATIONStockbasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/STOCKBASEDCOMPENSATIONStockbasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_d25978e7-153f-4ac0-81cd-0aa94c51a0fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_d8bd42a3-1621-4512-a93a-faf0b49132f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_d25978e7-153f-4ac0-81cd-0aa94c51a0fb" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_d8bd42a3-1621-4512-a93a-faf0b49132f7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_eb27de78-dbc4-4220-8616-6eb454bcc07b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_d8bd42a3-1621-4512-a93a-faf0b49132f7" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_eb27de78-dbc4-4220-8616-6eb454bcc07b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_eb27de78-dbc4-4220-8616-6eb454bcc07b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_eb27de78-dbc4-4220-8616-6eb454bcc07b" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_eb27de78-dbc4-4220-8616-6eb454bcc07b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_a5510615-8f50-4ae1-9f4d-5bc684fe1de8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_eb27de78-dbc4-4220-8616-6eb454bcc07b" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_a5510615-8f50-4ae1-9f4d-5bc684fe1de8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_905b7a5b-ef3d-410b-a99c-6d933530d69a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_a5510615-8f50-4ae1-9f4d-5bc684fe1de8" xlink:to="loc_us-gaap_CostOfSalesMember_905b7a5b-ef3d-410b-a99c-6d933530d69a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_2f2a9079-b900-4679-a69e-b87cdb0f2434" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_a5510615-8f50-4ae1-9f4d-5bc684fe1de8" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_2f2a9079-b900-4679-a69e-b87cdb0f2434" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_e4245e1d-8513-4d93-9407-ae845c29b98e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_a5510615-8f50-4ae1-9f4d-5bc684fe1de8" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_e4245e1d-8513-4d93-9407-ae845c29b98e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_8067ab00-0495-49b2-9e52-0c4489495b7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_a5510615-8f50-4ae1-9f4d-5bc684fe1de8" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_8067ab00-0495-49b2-9e52-0c4489495b7f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAbstract_81bc14a8-3a5c-4344-82ac-9bc8d6f56a6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_d25978e7-153f-4ac0-81cd-0aa94c51a0fb" xlink:to="loc_us-gaap_ShareBasedCompensationAbstract_81bc14a8-3a5c-4344-82ac-9bc8d6f56a6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_8c2bef49-330b-4ffd-bba8-8a81d3832212" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationAbstract_81bc14a8-3a5c-4344-82ac-9bc8d6f56a6f" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_8c2bef49-330b-4ffd-bba8-8a81d3832212" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/INCOMETAXESNarrativeDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#INCOMETAXESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/INCOMETAXESNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_acmr_IncomeTaxesLineItems_16f75778-fb84-4583-abe1-0dfa6e8e1fb5" xlink:href="acmr-20250930.xsd#acmr_IncomeTaxesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_IncomeTaxesTable_b8c87227-7af3-4f2b-9c83-b9c394516363" xlink:href="acmr-20250930.xsd#acmr_IncomeTaxesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_acmr_IncomeTaxesLineItems_16f75778-fb84-4583-abe1-0dfa6e8e1fb5" xlink:to="loc_acmr_IncomeTaxesTable_b8c87227-7af3-4f2b-9c83-b9c394516363" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_b78f2800-c009-4e88-9a5a-c4944c8a5fc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_acmr_IncomeTaxesTable_b8c87227-7af3-4f2b-9c83-b9c394516363" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_b78f2800-c009-4e88-9a5a-c4944c8a5fc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_b78f2800-c009-4e88-9a5a-c4944c8a5fc2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_b78f2800-c009-4e88-9a5a-c4944c8a5fc2" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_b78f2800-c009-4e88-9a5a-c4944c8a5fc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_f6ca1ac3-2e3e-4a40-a68b-50e5ee2d8f2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_b78f2800-c009-4e88-9a5a-c4944c8a5fc2" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_f6ca1ac3-2e3e-4a40-a68b-50e5ee2d8f2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_528c1a22-fd26-41ec-bb30-4c669e24ea23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_f6ca1ac3-2e3e-4a40-a68b-50e5ee2d8f2b" xlink:to="loc_us-gaap_ForeignCountryMember_528c1a22-fd26-41ec-bb30-4c669e24ea23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_82c309f3-0695-4433-aa1a-02732ce44b93" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_acmr_IncomeTaxesTable_b8c87227-7af3-4f2b-9c83-b9c394516363" xlink:to="loc_srt_ConsolidatedEntitiesAxis_82c309f3-0695-4433-aa1a-02732ce44b93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_82c309f3-0695-4433-aa1a-02732ce44b93_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_82c309f3-0695-4433-aa1a-02732ce44b93" xlink:to="loc_srt_ConsolidatedEntitiesDomain_82c309f3-0695-4433-aa1a-02732ce44b93_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_191f5343-ca85-4c99-a5b9-6e29c687cbe4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_82c309f3-0695-4433-aa1a-02732ce44b93" xlink:to="loc_srt_ConsolidatedEntitiesDomain_191f5343-ca85-4c99-a5b9-6e29c687cbe4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchShanghaiIncMember_59f14935-120e-4fba-8626-944a7b510197" xlink:href="acmr-20250930.xsd#acmr_ACMResearchShanghaiIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_191f5343-ca85-4c99-a5b9-6e29c687cbe4" xlink:to="loc_acmr_ACMResearchShanghaiIncMember_59f14935-120e-4fba-8626-944a7b510197" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchWuxiIncMember_02742531-3875-4227-9d59-894cd09d8fe1" xlink:href="acmr-20250930.xsd#acmr_ACMResearchWuxiIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_191f5343-ca85-4c99-a5b9-6e29c687cbe4" xlink:to="loc_acmr_ACMResearchWuxiIncMember_02742531-3875-4227-9d59-894cd09d8fe1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchBeijingIncMember_95ec2d9b-6771-4854-b458-cd72deec902a" xlink:href="acmr-20250930.xsd#acmr_ACMResearchBeijingIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_191f5343-ca85-4c99-a5b9-6e29c687cbe4" xlink:to="loc_acmr_ACMResearchBeijingIncMember_95ec2d9b-6771-4854-b458-cd72deec902a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchLingangInc.ACMLingangMember_9782309f-3ea2-40ad-8761-f9ce1f577aeb" xlink:href="acmr-20250930.xsd#acmr_ACMResearchLingangInc.ACMLingangMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_191f5343-ca85-4c99-a5b9-6e29c687cbe4" xlink:to="loc_acmr_ACMResearchLingangInc.ACMLingangMember_9782309f-3ea2-40ad-8761-f9ce1f577aeb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMShanghaiMember_e1e0bdaa-381a-4252-b82d-dcb6452a35ba" xlink:href="acmr-20250930.xsd#acmr_ACMShanghaiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_191f5343-ca85-4c99-a5b9-6e29c687cbe4" xlink:to="loc_acmr_ACMShanghaiMember_e1e0bdaa-381a-4252-b82d-dcb6452a35ba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_acmr_IncomeTaxesLineItems_16f75778-fb84-4583-abe1-0dfa6e8e1fb5" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_f76afe31-07ad-4535-a069-62b639695794" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnrecognizedTaxBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_f76afe31-07ad-4535-a069-62b639695794" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense_24190b7c-cb05-4605-a8f0-659a5148bb5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:to="loc_us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpense_24190b7c-cb05-4605-a8f0-659a5148bb5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ForeignCorporateTaxRate_09a34b92-aba4-4bda-99c9-d84131be7966" xlink:href="acmr-20250930.xsd#acmr_ForeignCorporateTaxRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:to="loc_acmr_ForeignCorporateTaxRate_09a34b92-aba4-4bda-99c9-d84131be7966" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_7e7e1a3b-1894-44d9-98d5-29df9de2c789" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_7e7e1a3b-1894-44d9-98d5-29df9de2c789" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAmortizationPeriod_a8d33b85-1dee-4aa2-a839-8a353278ee43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostAmortizationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:to="loc_us-gaap_CapitalizedContractCostAmortizationPeriod_a8d33b85-1dee-4aa2-a839-8a353278ee43" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_0332e968-463b-4660-8c2e-8f9c44c07f90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitContinuingOperationsAbstract_5972cd0d-8e8f-4813-aa3f-80dc4efd3384" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential_0332e968-463b-4660-8c2e-8f9c44c07f90" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/SEGMENTINFORMATIONDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#SEGMENTINFORMATIONDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/SEGMENTINFORMATIONDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_3c806c1a-cb65-407e-b81e-e26ab925bde5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_2fc598b6-cb2c-4851-be6c-c14cd1db1eb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3c806c1a-cb65-407e-b81e-e26ab925bde5" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_2fc598b6-cb2c-4851-be6c-c14cd1db1eb0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_9a2c22e8-ad14-45a3-8e00-ab6b8014f7d9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_2fc598b6-cb2c-4851-be6c-c14cd1db1eb0" xlink:to="loc_srt_StatementGeographicalAxis_9a2c22e8-ad14-45a3-8e00-ab6b8014f7d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_9a2c22e8-ad14-45a3-8e00-ab6b8014f7d9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_9a2c22e8-ad14-45a3-8e00-ab6b8014f7d9" xlink:to="loc_srt_SegmentGeographicalDomain_9a2c22e8-ad14-45a3-8e00-ab6b8014f7d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_b05df05d-687b-4aba-8c81-fa189bdf6a54" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_9a2c22e8-ad14-45a3-8e00-ab6b8014f7d9" xlink:to="loc_srt_SegmentGeographicalDomain_b05df05d-687b-4aba-8c81-fa189bdf6a54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_b88f6cdf-b9b4-42b6-a062-8268c61dcd0f" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_b05df05d-687b-4aba-8c81-fa189bdf6a54" xlink:to="loc_country_CN_b88f6cdf-b9b4-42b6-a062-8268c61dcd0f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_KR_28c34030-c880-4686-a7e1-583b65d33306" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_KR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_b05df05d-687b-4aba-8c81-fa189bdf6a54" xlink:to="loc_country_KR_28c34030-c880-4686-a7e1-583b65d33306" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_a8265707-1908-4837-ae71-9e34673496a9" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_b05df05d-687b-4aba-8c81-fa189bdf6a54" xlink:to="loc_country_US_a8265707-1908-4837-ae71-9e34673496a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicAreasLongLivedAssetsAbstract_a6fce5e3-495a-4847-97aa-f8156fa94b2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeographicAreasLongLivedAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3c806c1a-cb65-407e-b81e-e26ab925bde5" xlink:to="loc_us-gaap_GeographicAreasLongLivedAssetsAbstract_a6fce5e3-495a-4847-97aa-f8156fa94b2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncurrentAssets_7f0c7cdc-0bef-47f0-b23a-00f71e83c672" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GeographicAreasLongLivedAssetsAbstract_a6fce5e3-495a-4847-97aa-f8156fa94b2a" xlink:to="loc_us-gaap_NoncurrentAssets_7f0c7cdc-0bef-47f0-b23a-00f71e83c672" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://acmrcsh.com/role/STATUTORYSURPLUSRESERVEDetails" xlink:type="simple" xlink:href="acmr-20250930.xsd#STATUTORYSURPLUSRESERVEDetails"/>
  <link:definitionLink xlink:role="http://acmrcsh.com/role/STATUTORYSURPLUSRESERVEDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesLineItems_dcb48e97-1f31-46fb-b862-ffb4de144b11" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatutoryAccountingPracticesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesTable_1f1f28d3-b8ad-4fff-9600-2d6111a21780" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatutoryAccountingPracticesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatutoryAccountingPracticesLineItems_dcb48e97-1f31-46fb-b862-ffb4de144b11" xlink:to="loc_us-gaap_StatutoryAccountingPracticesTable_1f1f28d3-b8ad-4fff-9600-2d6111a21780" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_e3ded821-21d6-4d30-9bc4-68a4c12a72d9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatutoryAccountingPracticesTable_1f1f28d3-b8ad-4fff-9600-2d6111a21780" xlink:to="loc_srt_ConsolidatedEntitiesAxis_e3ded821-21d6-4d30-9bc4-68a4c12a72d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e3ded821-21d6-4d30-9bc4-68a4c12a72d9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_e3ded821-21d6-4d30-9bc4-68a4c12a72d9" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e3ded821-21d6-4d30-9bc4-68a4c12a72d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_b227a952-2b0b-40b9-8431-e8d7f5996fbb" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_e3ded821-21d6-4d30-9bc4-68a4c12a72d9" xlink:to="loc_srt_ConsolidatedEntitiesDomain_b227a952-2b0b-40b9-8431-e8d7f5996fbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_ACMResearchShanghaiIncMember_cbf712a7-67ca-4565-82dc-7e1e9c83f3e2" xlink:href="acmr-20250930.xsd#acmr_ACMResearchShanghaiIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_b227a952-2b0b-40b9-8431-e8d7f5996fbb" xlink:to="loc_acmr_ACMResearchShanghaiIncMember_cbf712a7-67ca-4565-82dc-7e1e9c83f3e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficitAbstract_4b7f8949-de15-4f9a-a937-56dbe3822840" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficitAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatutoryAccountingPracticesLineItems_dcb48e97-1f31-46fb-b862-ffb4de144b11" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficitAbstract_4b7f8949-de15-4f9a-a937-56dbe3822840" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance_c5aed4f4-f77b-4519-abba-05caa5333878" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetainedEarningsAccumulatedDeficitAbstract_4b7f8949-de15-4f9a-a937-56dbe3822840" xlink:to="loc_us-gaap_StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance_c5aed4f4-f77b-4519-abba-05caa5333878" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_HowardChenMember_57a7ba5a-830c-4b31-ac3e-98713f9231eb" xlink:href="acmr-20250930.xsd#acmr_HowardChenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_acmr_HowardChenMember_57a7ba5a-830c-4b31-ac3e-98713f9231eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_FupingChenMember_e138ff5a-9aae-49c2-a716-239a0acde651" xlink:href="acmr-20250930.xsd#acmr_FupingChenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_acmr_FupingChenMember_e138ff5a-9aae-49c2-a716-239a0acde651" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_MarkMcKechnieMember_6b5f9f33-2b82-4f1d-8758-90ae9ab3bfa6" xlink:href="acmr-20250930.xsd#acmr_MarkMcKechnieMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_acmr_MarkMcKechnieMember_6b5f9f33-2b82-4f1d-8758-90ae9ab3bfa6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_HaipingDunMember_b9159ec3-6614-4a1e-8922-79dd406946c7" xlink:href="acmr-20250930.xsd#acmr_HaipingDunMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_acmr_HaipingDunMember_b9159ec3-6614-4a1e-8922-79dd406946c7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_acmr_LisaFengMember_9106a4f4-b850-4377-943f-8ac210db7596" xlink:href="acmr-20250930.xsd#acmr_LisaFengMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_acmr_LisaFengMember_9106a4f4-b850-4377-943f-8ac210db7596" xlink:type="arc" order="6"/>
  </link:definitionLink>
</link:linkbase>
