Aiming at problems caused by the use of filter in the high-frequency injection method of PMSM in the low-speed condition. such as limiting the system bandwidth, reducing the dynamic performance, phase lag, amplitude attenuation and so on, this paper proposes an improved signal extraction method of high-frequency square wave injection without magnetic pole identification. By changing the frequency of the high-frequency signal to a quarter of the inverter switching frequency, the filter is avoided and the use the Luenberger Observer for position information acquisition This method can accurately obtain the rotor position and the dynamic performance of the system is improved. Simulation results verify the effectiveness of the improved algorithm.