<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-01-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000717238</issuerCik>
        <issuerName>MSC SOFTWARE CORP</issuerName>
        <issuerTradingSymbol>MNSC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001310679</rptOwnerCik>
            <rptOwnerName>Spivy Gregory P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE, FOURTH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001129787</rptOwnerCik>
            <rptOwnerName>VA PARTNERS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>FOURTH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Nonqualified Stock Option Award (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.8</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-01-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2007-01-03</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-03</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Formula grant to non-employee director of nonqualified option to buy common stock under Issuer's 2001 Stock Option Plan.</footnote>
        <footnote id="F2">Option grant becomes 100% exercisable on the first anniversary of the date the option was granted.</footnote>
        <footnote id="F3">Column 8 is not a required reportable field.</footnote>
        <footnote id="F4">Under an agreement with ValueAct Capital Master Fund, L.P., Gregory P. Spivy is deemed to hold the options for the benefit of ValueAct Capital Master Fund, L.P., ValueAct Capital Partners Co-Investors, L.P. and indirectly for VA Partners, LLC as general partner of ValueAct Capital Master Fund, L.P. and ValueAct Capital Partners Co-Investors, L.P.  Gregory P. Spivy is a director of MSC.Software.  Jeffrey W. Ubben, Peter H. Kamin and George F. Hamel are Managing Members of VA Partners, LLC, the General Partner of ValueAct Capital Master Fund, L.P. and ValueAct Capital Partners Co-Investors, L.P. The reporting persons disclaim beneficial ownership of the reported options except to the extent of their pecuniary interest therein.</footnote>
    </footnotes>

    <remarks>Name: ValueAct Capital Master Fund, L.P.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA  94133
Designated Filer: Gregory P. Spivy
Issuer and Ticker Symbol: MSC.Software Corporation (MNSC)
Date of Event Requiring Statement: January 3, 2006

Name: ValueAct Capital Partners Co-Investors, L.P.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA  94133
Designated Filer: Gregory P. Spivy
Issuer and Ticker Symbol: MSC.Software Corporation (MNSC)
Date of Event Requiring Statement: January 3, 2006

Name: VA Partners, L.L.C.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA  94133
Designated Filer: Gregory P. Spivy
Issuer and Ticker Symbol: MSC.Software Corporation (MNSC)
Date of Event Requiring Statement: January 3, 2006

Name: George F. Hamel, Jr.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA  94133
Designated Filer: Gregory P. Spivy
Issuer and Ticker Symbol: MSC.Software Corporation (MNSC)
Date of Event Requiring Statement: January 3, 2006

Name: Jeffrey W. Ubben
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA  94133
Designated Filer: Gregory P. Spivy
Issuer and Ticker Symbol: MSC.Software Corporation (MNSC)
Date of Event Requiring Statement: January 3, 2006

Name: Peter H. Kamin
Address: 265 Franklin Street, 16th Floor, Boston, MA 02110
Designated Filer: Gregory P. Spivy
Issuer and Ticker Symbol: MSC.Software Corporation (MNSC)
Date of Event Requiring Statement: January 3, 2006</remarks>

    <ownerSignature>
        <signatureName>By: /s/ Gregory P. Spivy</signatureName>
        <signatureDate>2006-01-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>VALUEACT CAPITAL MASTER FUND, L.P., BY VA PARTNERS, L.L.C., ITS GENERAL PARTNER By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2006-01-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>VALUEACT CAPITAL PARTNERS CO-INVESTORS, L.P., BY VA PARTNERS, L.L.C., ITS GENERAL PARTNER By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2006-01-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>VA PARTNERS, L.L.C. By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2006-01-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>By: /s/ Jeffrey W. Ubben</signatureName>
        <signatureDate>2006-01-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>By: /s/ George F. Hamel, Jr.</signatureName>
        <signatureDate>2006-01-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>By: /s/ Peter H. Kamin</signatureName>
        <signatureDate>2006-01-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
