For overcoming the deficiencies of the existing bearing rotor system dynamic model, a nonlinear lumped mass model of ball bearing flexible rub rotor system is established, in which the nonlinear ball bearing force, unbalance, rubbing fault and gyroscopic effect are considered. Based on the numerical calculation and comparison, some conclusions can be obtained. The rotor system response is variable stiffness vibration of the ball bearing under low speed. Comparing with that of high speed the variable stiffness vibration of the ball bearing weaken. The influence of the rotor unbalance and rubbing fault on rotor system is strengthened gradually. The gyroscopic effect on high speed symmetric rotor response is important.