In order to improve the dynamic performance of threephase permanent magnet synchronous motor (PMSM) speed control system improve the control performance of traditional sliding mode speed controller, suppress the system chattering, and improve the control precision, an improved sliding mode speed controller based on a newtype reaching law and a load observer was designed. MATLAB/Simulink simulation software was used to build the control system model and conduct simulation analysis. The design was verified by simulation. Good speed tracking precision and load disturbance resistance were obtained, and stability and robustness of the system were improved.