A　nonlinear　dynamic　model　of　spindle-cutter　coupling　system　under　cutting　force,　which　takes　into　account　the　cutter　stiffness　and　the　nonlinearity　of　bearing　clearance,　is　established.　Analysis　of　the　cross-section　of　a　two-flute　end　mill　is　conducted　to　determine　cutter　stiffness.　Then,　the　calculated　cutter　stiffness　is　introduced　into　the　nonlinear　dynamic　model　of　coupling　system.　In　the　modeling　of　cutting　force,　the　cutting　width　takes　into　account　the　cutter　tip　displacement.　Moreover,　nonlinear　dynamic　characteristics　of　spindle-cutter　coupling　system　are　studied　and　the　effects　of　bearing　clearance　on　the　response　of　cutter　tip　are　discussed　as　well,　considering　unbalanced　force.　The　numerical　results　show　that　the　bearing　clearance　strongly　affects　the　equilibrium　position.　With　different　values　of　bearing　clearance　and　rotation　speed,　the　responses　of　cutter　tip　exhibit　periodic,　quasi-periodic　and　chaotic　characteristics.　Dynamic　characteristics　of　spindle-cutter　system　depends　on　the　bearing　clearance　and　rotation　speed.　The　proper　bearing　clearance　and　rotation　speed　should　be　chosen　to　ensure　a　stable　cutting　and　high　cutting　rate　according　to　the　bifurcation　diagram.　The　response　of　the　cutter　tip　is　a　quasi-periodic　motion　when　the　cutting　force　is　considered.　The　time-domain　response　of　cutter　tip　predicted　by　nonlinear　dynamic　analysis　can　provide　the　basis　for　machining　error　prediction.