Due to the nonlinearity of the inverter and the air gap magnetic field distortion of permanent magnet synchronous motor (PMSM), the stator current contains a large amount of harmonic components during the operation of the PMSM, which caused the current waveform to be distorted, resulting in a large torque ripple. The traditional harmonic suppression method used lowpass filter (LPF) to extract the 5th and 7th harmonic components, so that the dynamic response time was long and the steadystate error was large. Aiming at this problem, the closedloop current average method was proposed to extract the harmonic components. The simulation results showed that the current average method could improve the system’s rapidity and stability. Applying the closedloop current average method to the PMSM harmonic suppression system, the simulation results showed that the harmonic voltage injection method based on the closedloop current average method could reduce the distortion rate of the current waveform and the 5th and 7th harmonics content.