Abstract: For the characteristics of permanent magnet synchronous motor DTC in the traditional digital control under , based on the analysis of the amplitude of stator flux and torque angle and torque variation, in order to reduce the torque ripple during stable operation and reduce the start time, study the control performance with null vector DTC, and compared with the traditional DTC from the angle of simulation. The optimal action interval of the null vector is determined, and the lower torque ripple is guaranteed when the motor is running stably, and the motor has a shorter start time.