A speed control strategy based on integral sliding-mode was proposed to solve the problems such as poor control, large fluctuation and slow dynamic response of the output speed of servo motor system; the load torque observer was designed to resolve the load disturbance in the control process; the permanent magnet synchronous motor speed control model was established on the basis of the Simulink; the test system of motor was built to test and verify the steady-state performance and dynamic performance of the control system respectively. Experimental results show that, compared with the traditional proportion integration differentiation control and the ordinary SMC(sliding mode variable structure control), the designed control strategy can improve the robustness and rapidity of the system significantly and the chattering phenomenon of SMC control can be inhibited.