In view of the existential problems of many parameters to be adjusted and unclear physical meaning of parameters in the control of permanent magnet synchronous motor based on active disturbance rejection principle, an improved sliding mode active disturbance rejection control algorithm has thus been proposed. Firstly, the optimal control function is constructed by using the sliding mode reaching law, with the fal function in the extended state observer and non-linear error feedback control law to be replaced by the optimal control function, thus reducing the parameters to be adjusted and optimizing the structure of the non-linear ADRC. Secondly, Lyapunov function is used for an analysis of the stability of the improved sliding mode ADRC. Finally, Matlab simulation is used for the verification of the feasibility of the algorithm. The simulation results show that the improved sliding mode ADRC can not only retain the advantages of non-overshoot starting and strong anti-load disturbance ability of non-linear ADRC method, but also improve the dynamic and steady-state performance of permanent magnet synchronous motor speed regulation system.