Abstract: In order to expand running speed scope of permanent magnet synchronous servo motor, a switching method of winding series-parallel was proposed in this paper, the implementation of the method was also described in details, and the static and dynamic simulation of the method was also realized. The simulation results show that switching method of winding series-parallel can greatly expand running speed scope of the permanent magnet synchronous servo motor on the premise of the motor at low speed and high speed performance, and can solve the contradiction about high torque at low speed and high speed large power of the same motor.