the basic principle of direct torque control is analyzed, and the application of NPC three-level inverter in direct torque control is studied. on the basis of composite vector, an optimization method of composite vector is proposed, which can effectively suppress the fluctuation of NPC three-level DC side midpoint potential. finally, an independent functional module is established in Matlab/Simulink, and the simulation model of permanent magnet synchronous motor direct torque control system is built. Simulation results show that this method is reasonable and effective.