<?xml version="1.0" encoding="utf-8"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
  <periodOfReport>2003-12-12</periodOfReport>
  <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001082114</issuerCik>
        <issuerName>LIBERTY MEDIA CORP /DE/</issuerName>
        <issuerTradingSymbol>L, LMC.B</issuerTradingSymbol>
  </issuer>
  <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000937797</rptOwnerCik>
            <rptOwnerName>MALONE JOHN C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O LIBERTY MEDIA CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>12300 LIBERTY BLVD.</rptOwnerStreet2>
            <rptOwnerCity>ENGLEWOOD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80112</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
      <isDirector>1</isDirector>
      <isOfficer>1</isOfficer>
      <isTenPercentOwner>1</isTenPercentOwner>
      <isOther>0</isOther>
      <officerTitle>Chairman of the Board</officerTitle>
    </reportingOwnerRelationship>
  </reportingOwner>
  <nonDerivativeTable>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Series B Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2003-12-12</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>P</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>800</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>11.52</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>A</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>69225199</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>D</value>
        </directOrIndirectOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Series B Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>5281739</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>By a limited liability company, as sole member</value>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Series B Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>8699963</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>By GRAT</value>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Series B Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>9511690</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>By GRAT</value>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Series B Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>12204124</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>By GRAT</value>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
    <nonDerivativeHolding>
      <securityTitle>
        <value>Series B Common Stock</value>
      </securityTitle>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>3409436</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>By spouse</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeHolding>
  </nonDerivativeTable>
  <footnotes>
    <footnote id="F1">The reporting person disclaims beneficial ownership of these securities, and this report shall not be deemed an admission that the Reporting Person is the beneficial owner of the securities for the purpose of Section 16 or for any other purpose.</footnote>
  </footnotes>
  <ownerSignature>
    <signatureName>/s/ Charles Y. Tanabe, Attorney-in-fact</signatureName>
    <signatureDate>2003-12-16</signatureDate>
  </ownerSignature>
</ownershipDocument>

