Permanent magnet synchronous motor (PMSM) had many problems such as frequent overshoot, slow response time and so on when using direct torque control (DTC) scheme based on space vector modulation. The traditional speed PI controller and torque PI controller were replaced with the supertwisting sliding mode controller and it was proved that the supertwisting sliding mode controller used in speed loop and torque loop could converge in finite time theoretically. The torque ripple and dynamic response speed of PMSM was studied by MATLAB/Simulink simulation software. The simulation results showed that the supertwisting sliding mode controller and PI controller in DTC of space vector compared with smaller torque ripple, high dynamic response speed and solves the problem of frequent overshoot.