The　free　energy　and　dissipation　function　for　over　consolidated　clays　are　established,　which　are　based　on　the　generalized　thermodynamic　method　and　combined　with　the　thermodynamic　functions　form　of　the　modified　Cam　model.　The　energy　generated　by　the　plastic　shear　deformation　is　considered　a　part　of　free　energy　in　the　free　energy　function,　and　this　partial　free　energy　is　related　to　the　degree　of　over　consolidation.　When　the　degree　of　over　consolidation　decreases,　the　free　energy　generated　by　the　plastic　shear　deformation　also　decreases.　The　dissipation　function　is　independent　of　the　current　stress　state,　so　the　associated　flow　rule　is　still　employed　in　this　paper.　Based　on　the　free　energy　function　and　the　dissipation　function,　all　of　the　yield　function,　the　flow　law,　the　hardening　law　and　the　elastic　law　can　be　obtained　with　strict　mathematical　derivation　from　the　two　scalar　functions.　The　final　elastic-plastic　incremental　relation　can　then　be　obtained.　Finally,　the　rationality　of　the　model　is　verified　by　comparing　the　calculation　and　experimental　results　in　stress　and　strain,　volumetric　strain　of　four　different　over　consolidation　clays.　©　2019,　Science　Press.　All　right　reserved.