In order to study the vibration characteristics of highspeed permanent magnet motor under high speed operating conditions, it was simplified to a rotorbearing system, a mathematical model was established, and the effects of supporting stiffness, damping, acceleration and supporting position on the rotor vibration characteristics were calculated by Runge-Kutta method. Research results show that the changing bearing stiffness can change the value of critical speed, but can’ t change the critical speed corresponding to the maximum amplitude；increasing damping can reduce the amplitude values, but can’ t change the critical speed of the system; increasing rotor acceleration can reduce the maximum vibration amplitude, but it will increase the control torque of the system; the vibration amplitude produced by y direction bearing position change is larger than that of x direction bearing position change, and the bearing near the location of the thrust bearing plate produces big amplitude. Finally, the vibration amplitude can be controlled by reducing acceleration and stiffness, to avoid the resonance region.