In　the　mechanical　products,　there　are　always　some　poor　stiffness　and　high　precision　thin-walled　workpieces　which　will　produce　deformation　in　the　machining　process　easily,　so　it　is　difficult　to　control　the　machining　accuracy　and　to　meet　the　requirement　of　higher　machining　accuracy.　Based　the　finite　element　numerical　simulation　key　technology,　this　paper　analyzes　the　machining　deformation,　including　geometric　model　simplification,　mode　selection,　dynamic　loading,　a　3D　simulation　model　of　thin　plate　features　establishment.　Through　the　finite　element　numerical　simulation　analysis　of　the　thin　plate,　we　analyze　the　influence　on　processing　deformation　from　different　processing　parameters　and　different　constraints.　©　(2014)　Trans　Tech　Publications,　Switzerland.