In the sensorless control of permanent magnet synchronous motor based on sliding mode observer (SMO), the observation error of position and speed was large and the chattering was strong. In order to solve this problem, the traditional SMO was analyzed. A kind of nonsingular fast terminal sliding mode surface was studied, and a sliding mode control law with integral was discussed, which could effectively improve the observation accuracy, reduce chattering and eliminate the low pass filter and rotor position compensation. The stability of the observer was proved by Lyapunov function. Finally, MATLAB/Simulink software was used for simulation, and the results showed that the control performance of the proposed observer was better than that of the traditional SMO.