In order to solve the problems of low working efficiency and the out of synic of motor speed of the Sitai Mine, the direct torque control system was adopted, the structure and working principle of the motor control system were expounded, the voltage vector, service life and power balance of belt conveyor motor were analyzed. Three - phase current and motor speed are simulated. The theoretical analysis and simulation research showed that the direct torque control system could improve the balance of motor work, realize stepless speed regulation, solve the problem of low work efficiency and motor speed synchronization.