Abstract: To control and accurately calculate support stiffness and critical speed,numerical calculation models have been established,which considered the mixed preload mechanism of angular contact ball bearing.Taking a spindle system as finite element model,bearing group model and shaft model were coupled to structure the shaft-bearing model.The coupled model was iterated to obtain spindle system dynamic parameters,and then the whirl frequency of spindle was analyzed.The shaft-bearing model dynamics calculation process was set up,and the support stiffness and whirl frequency of spindle was researched in different preload mechanism.Theoretical calculation results show that compared with the traditional method,this model has higher precision to predict high speed spindle dynamic characteristics in operation.Adopting reasonable preload method and selecting proper preload force is conducive to improve the critical frequency of spindle system in operation.