This essay introduces the ac servo system of the permasyn motor, and put forward a new control strategy based on SVM-DTC, aiming at the torque pulsation of the direct torque control(DTC). This strategy uses component of electron voltage in the stator flux linkage coordinate to control electromagnetic torque and flux linkage, integrating SVPWM to control the switch of inverter. Besides, hardware platform is built using DSP2812. According to the simulation of MatLab and the wave form of the test, SVM-DTC can reduce the fluctuation of torque and flux linkage.