Aiming at the defects of dynamic sliding surface and variable exponential asymptotic law, a new integral sliding mode speed controller was studied. And the designed controller was improved by combining with the switch function, which new was applied in the speed loop in servo system of permanent magnet synchronous motor. The servo system simulation model was built by the Matlab. The simulation results show that the designed new sliding mode controller is better than the traditional PI and variable exponent sliding mode control in speed adjusting performance. It can not only effectively restrain the inherent chattering of the sliding mode variable structure, but also enhance the rapidity and robustness of the control system.