In order to study the influence of combination of wheel radius difference on the dynamic performance of metro vehicles,the nonlinear dynamic model of a metro vehicle was established based on the vehicle system dynamics and Hertz nonlinear contact theory,and the critical speed,Sperling value,safety and wear power of the metro vehicle under various wheel diameter difference combinations were analyzed.The results show that under the combined conditions of various wheel radius difference,the critical speed of metro vehicle is greatly reduced,and the lateral Sperling value and wear power of the metro vehicles are significantly increased with the increase of wheel radius difference.The vertical Sperling value of the metro vehicle,the lateral wheelset force,the wheelrail vertical force,the derailment coefficient and the wheel unloading rate are little effected by the wheel radius difference.When passing the right curve and the left curve,though the wear power of the metro vehicle are all increased,but different in the increase numerical value with the wheel radius difference increased.