In order to improve the control performance of permanent magnet synchronous motor (PMSM) drive system, a siding mode speed control strategy based on an improved reaching law method was proposed. To shorten the reaching time and weaken system chattering of the conventional exponential reaching law, a novel reaching law based on traditional reaching law was proposed, and the method was applied to PMSM drive system. Compared with traditional PI controller, simulation and experiment results showed that the proposed controller improve the system robustness and dynamic performance.