In order to improve the problems of high-frequency chattering, phase delay, and low-speed failure in traditional sliding mode observers (SMO), this paper proposes an improved SMO control strategy. This method introduces an amplification factor before the lowpass filter to amplify the back-EMF signal for easy extraction and estimation; adopts the hyperbolic tangent function as the sign function to reduce the high-frequency chattering and signal interference of the system; adopts an adaptive filter to improve detection Accuracy, reduce phase delay. Through MATLAB/ Simulink simulation analysis, the two strategies of improved SMO and traditional SMO are compared. The results show that the improved SMO reduces the phase delay time by 97. 5% compared with the traditional SMO, and it can significantly reduce chattering phenomenon, and accurately estimate the motor below the speed of 20 r/ min. , to achieve good estimation performance at full speed, indicating that the improved SMO strategy has better estimation accuracy and adaptability.