A co-simulation method of the FEM software ANSYS and multi-body dynamics software SIMPACK was introduced. The wheelsets was taken as flexible bodies with FEM structure and mode, and carbody and frame as rigid ones; In the SIMPACK, rigid-flexible coupled dynamics model of a complete railway vehicle system was established. The dynamic characteristics of flexible wheelset model and rigid wheelset model were compared and analyzed. The results showed that: wheelsets flexible characteristics influenced vehicle dynamics little at lower speed linear running but should be considered at high speed; when passing a curve, calculation result of flexible wheelsets model was less better than the rigid ones, which was agree to the practice.