Abstract: Sensorless control of interior permanent magnetic synchronous machine is mainly adopt the sinusoidal signal injection method. However, filters are needed for extracting the high frequency current signals for position estimation, which make single delay and sacrifice the bandwidth of current control loop. And the dynamic control performance is severely affected. An improved high-frequency square wave injection method was proposed to solve these problems by separating the injection period and the FOC period so low-pass filters and band-pass filters are not needed. But estimation accuracy is reduced by the effect of the inverter nonlinearity when estimate the rotor position. To solve these problems, a new high-frequency square-wave injection method that can suppress the nonlinearity of inverter was proposed. This method suppresses the high-frequency distortion voltage caused by inverter non-linearity by injecting different amplitudes voltage, so that improve the estimation accuracy of the rotor position angle. The simulation and comparison experiments results show that the proposed method can reduce the position estimation error from ±11° to ±3°, and it has good stability and robustness.