Radial　gap　will　occur　at　the　spindle-tool　holder　interface　when　the　spindle　rotates　at　high　speed.　Therefore,　the　radial　gap　will　lead　to　the　nonlinear　stiffness　at　the　spindle-tool　holder　connection,　and　it　will　have　effects　on　dynamic　characteristic　of　spindle　system.　In　this　research,　classic　elastic　theory　is　adopted　to　evaluate　the　nonlinear　stiffness　at　spindle-tool　holder　interface.　Dynamic　model　of　spindle　system　is　established　considering　the　nonlinear　stiffness　at　spindle-tool　holder　interface.　The　fourth-order　Runge-Kutta　method　is　applied　to　solve　dynamic　response　of　the　spindle　system.　On　that　basis,　effects　of　drawbar　force　on　dynamic　characteristic　of　the　system　are　investigated.　Considering　the　cutting　force,　effects　of　rotational　speed　on　dynamic　response　of　cutter　tip　are　also　discussed.　The　numerical　results　show　that　the　drawbar　force　has　effects　on　vibration　mode　of　cutter　tip.　Chaotic　motion　will　not　occur　within　the　range　concerned　in　engineering　practice.　Considering　the　cutting　force,　the　motion　of　cutter　tip　turns　to　be　chaotic.　The　proper　rotational　speed　and　drawbar　force　should　be　chosen　to　ensure　a　stable　cutting　according　to　the　response　of　cutter　tip.