According　to　the　deformation　mechanism　of　mechanical　parts　in　the　process　of　the　stereolithography　rapid　prototyping　(SL-RP)　and　the　theory　of　temperature　stress　of　thin　plate　with　small　deflection,　the　distortion　deformation　of　the　plate　parts　is　studied　and　the　mechanical　equivalent　model　of　resin　phase　change　shrinkage　in　SLRP　is　presented.　The　time-varying　stiffness　of　the　slab　and　equivalent　force　of　resin　phase　change　shrinkage　in　SL-RP　are　derived　by　using　above　conclusions　and　the　commercial　FEM　(Finite　element　method)　package　ABAQUS,　the　numerical　simulation　of　parts　deformation　in　SL-RP　is　carried　out.　The　numerical　results　are　consistent　with　the　experimental　ones.　That　shows　that　it　is　reasonable　for　using　temperature　stress　to　simulated　the　shrinkage　of　resin　phase　change　and　it　is　appropriate　for　numerical　simulation　of　parts　deformation　by　using　this　mechanical　equivalent　model.　So　the　real　deformation　forecast　of　rapid　prototyping　parts　can　be　performed　by　using　this　model.