Sliding mode variable structure control (SMVSC) has very strong robustness, which has been widely applied in permanent magnet synchronous motor (PMSM) speed regulating system. Constant rate reaching law approach speed is related to the sliding mode reaching gain. The higher the sliding mode reaching gain, the faster the reaching speed, and then the stronger chattering. In this paper, a new reaching law is designed on the basis of constant reaching law. With the analysis of MATLAB, the new reaching law not only increases the approach speed of the sliding mode, but also has a better inhibition effect on chattering. It provides a reference for further experiments.