To improve the dynamic quality of the PMSM servo system, a generalized super-twisting sliding mode control strategy based on the sinusoidal saturation function is proposed in this paper. Firstly, the dynamic mathematical model of PMSM is established. Then, a sliding mode variable structure speed controller is designed based on the generalized super-twisting algorithm. To weaken the chattering phenomenon, the sinusoidal saturation function is used instead of the sign function. Finally, the effectiveness of the proposed strategy was verified by MATLAB/Simulink simulation platform and compared with GSTA-SMC, STA-SMC and SMC based on exponential reaching law, the proposed strategy improved the response speed and immunity of the system while reducing chattering.