Thermal　deformation　of　high-speed　motorized　spindle　has　an　important　effect　on　improving　the　machining　accuracy.　In　this　paper　the　thermal　boundary　conditions　of　thermal　deformation,　including　the　heat　generation　of　the　motor　and　bearing　and　heat　transfer　coefficient,　are　calculated　to　simulate　the　steady-state　temperature　field　distribution,　transient　thermal　analysis　and　thermal　deformation　in　ANSYS　Workbench.　They　provide　theoretically　the　data　for　the　thermal　error　compensation　of　the　spindle　system.