<?xml version="1.0"?><ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-10-01</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0000840883</issuerCik><issuerName>BTU INTERNATIONAL INC</issuerName>        <issuerTradingSymbol>BTUI</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001224721</rptOwnerCik><rptOwnerName>WRINN JOSEPH F</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>5 HOLLYWOOD ROAD</rptOwnerStreet1><rptOwnerStreet2></rptOwnerStreet2><rptOwnerCity>WINCHESTER</rptOwnerCity><rptOwnerState>MA</rptOwnerState><rptOwnerZipCode>01890</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeTable><derivativeTransaction><securityTitle><value>Options (right to buy)</value></securityTitle><conversionOrExercisePrice><value>2.53</value></conversionOrExercisePrice><transactionDate><value>2003-10-01</value></transactionDate><deemedExecutionDate><value>2003-10-01</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>1976</value></transactionShares><transactionPricePerShare><value>2.53</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-10-01</value></exerciseDate><expirationDate><value>2008-10-01</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>1976</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>17079</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes></footnotes><remarks></remarks><ownerSignature><signatureName>Joseph F. Wrinn</signatureName><signatureDate>2003-10-02</signatureDate></ownerSignature></ownershipDocument>

