The sliding mode control (SMC) system based on the traditional exponential reaching law was widely used in the permanent magnet synchronous motor (PMSM) speed control system. However, this algorithm had obvious buffeting when the SMC system was approaching, and its control precision could not cope with the complicated situation. In order to suppress the system buffeting and improve the dynamic and steadystate performance of the PMSM speed control system, a new reaching law was proposed based on the traditional exponential reaching law by introducing the weighted integral gain. The introduction of the weighted integral gain made the system sliding mode function and its integral result close to zero in the sliding mode, which effectively suppressed system buffeting. According to the proposed new reaching law, the speed controller was designed and applied to the PMSM vector control system. The new reaching law control strategy was compared with the traditional exponential reaching law control strategy in software simulation and hardware experiments respectively to verify the feasibility and effectiveness of the proposed control strategy.