Abstract: To improve dynamic quality of permanent magnet synchronous motor（PMSM） speed servo system,a novel exponent reaching law was proposed.Different from the conventional exponential reaching law,the reaching speed of novel reaching law was associated with the changes of the system state;the novel exponential reaching law can overcome the disadvantage of traditional reaching law,suppress the chattering and improve the reaching speed.The novel reaching law was applied to the PMSM speed servo system;a novel speed controller was designed to replace the traditional PI regulator.Simulation and experimental results show that the novel speed controller can improve steady,dynamic performances and robustness characteristics of speed servo system.