In order to improve the dynamic quality of permanent magnet synchronous motor (PMSM) speed regulation system, a novel sliding mode speed control algorithm based on variable exponential reaching law is proposed. Based on conventional exponential reaching law, variable exponential function and hyperbolic tangent function are introduced to improve the system adaptive adjustment ability of sliding mode approaching speed and suppress chattering effectively. Based on the novel variable exponential reaching law, the sliding mode speed controller of PMSM is designed. Simulation results show that, compared with conventional sliding mode speed controller and PI controller, the novel sliding mode speed controller can effectively improve speed tracking accuracy and anti disturbance capability.