Based on the elastic wheelset, wheel polygonization rigid-flexible coupling vehicle dynamics simulation model was established. Firstly, reasonableness of elastic wheelset was analyzed; then, by modifying command to form polygonal wheel, influence of elastic wheelset polygonization parameters-wave depth, phase angle and harmonic order to vehicle dynamics performance at different running speed was researched, and important indicators of the horizontal force of the axle, the wheel-rail lateral force, derailment coefficient, wheel load reduction rate were given at the speed of 40~80 km/h, which determined the critical speed. Simulation results showed that the three polygonization parameters effected on dynamics performance differently, but all had little impact on the derailment coefficient, and wheel load reduction rate had great impact at the speed of 60 km/h, so long-term operation at 60 km/h should be avoided to prevent resonance.