Abstract: Aiming at the problem that the traditional vector control method is difficult to obtain accurate rotor position and speed, a speed research method of permanent magnet synchronous motor based on high frequency square wave injection method and improved Luenberger observer is proposed. Because of the poor stability of the high-order system, the microcomputer control is difficult. Besides, the parameters in the high-order transfer function are highly dependent on the motor parameters and controller parameters, it is difficult to have general control performance for permanent magnet synchronous motor. In order to solve these problems, the electromagnetic torque feedforward term in the Luenberger observer is replaced by a second-order system composed of speed commands, and the second-order system is obtained by the least square method. Simulation results show that the improved scheme has better tracking accuracy and robustness under load disturbance.