<SUBMISSION>
<ACCESSION-NUMBER>0001422750-10-000001
<TYPE>4/A
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20080314
<FILING-DATE>20100331
<DATE-OF-FILING-DATE-CHANGE>20100331
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Brak Philippe
<CIK>0001422750
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4/A
<ACT>34
<FILE-NUMBER>333-43089
<FILM-NUMBER>10718926
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>GSI GROUP CORPORATION
<STREET2>39 MANNING ROAD
<CITY>BILLERICA
<STATE>MA
<ZIP>01821
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>GSI GROUP INC
<CIK>0001050925
<ASSIGNED-SIC>3523
<IRS-NUMBER>370856587
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>1004 EAST ILLINOIS ST
<CITY>ASSUMPTION
<STATE>IL
<ZIP>62510
<PHONE>2172264421
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1004 EAST ILLINOIS ST
<CITY>ASSUMPTION
<STATE>IL
<ZIP>62510
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2008-03-14</periodOfReport>

    <dateOfOriginalSubmission>2008-03-21</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001050925</issuerCik>
        <issuerName>GSI GROUP INC</issuerName>
        <issuerTradingSymbol>GSIGQ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001422750</rptOwnerCik>
            <rptOwnerName>Brak Philippe</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>GSI GROUP CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>125 MIDDLESEX TURNPIKE</rptOwnerStreet2>
            <rptOwnerCity>BEDFORD</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01730</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President/General Mgr.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-03-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">25,000 time-based shares vest in three equal annual installments beginning on March 14, 2009.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Philippe Brak by Anthony J. Bellantuoni, Attorney-In-Fact</signatureName>
        <signatureDate>2010-03-31</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
