The work aims to improve the response accuracy and speed of the permanent magnet synchronous motor during operation and optimize its dynamic feedback performance, to solve the problem of the contradiction between the reaching time and the system jitter in the traditional sliding mode control. In the experiment, a three-closed-loop control structure was used, in which a fuzzy PID control method was adopted for the position loop and current loop, and an improved sliding mode control method based on the new reaching law was adopted for the speed loop. Then, a disturbance observer was applied and the disturbance compensation was given to the system. According to the simulation results and the in-the-loop hardware test results, compared with the traditional three-closed-loop sliding mode control, the rotor position response speed of the proposed control method was 0.123 seconds faster and there was no overshoot within the same time, and the electromagnetic torque fluctuation amplitude was significantly reduced. The new reaching law designed effectively solves the problems existing in the traditional sliding mode control, and the established control system effectively improves the response accuracy and speed of the permanent magnet synchronous motor, weakens the jitter degree of the PMSM during operation, and provides good robustness.