Abstract: Under certain load or fault conditions, the motor matrix of underground belt conveyor may change suddenly, resulting in system instability, which affects the control accuracy. Therefore, the research on direct torque control of underground belt conveyor based on PLC variable frequency speed regulation technology is put forward. By presetting reasonable assumptions and using voltage balance equation and electromagnetic torque formula, the motor model ofunderground belt conveyor is constructed. Based on PLC variable frequency speed regulation technology, combined with the motor model of underground belt conveyor, the conveyor speed is controlled. By analyzing the parameters of motor angular acceleration, load torque and so on, the control constraint conditions of conveyor drive motor are set up. Euler's formula is used to discretize the stator flux equation, predict the stator flux and electromagnetic torque, construct the objective function to select the optimal switching state, and realize the direct torque control. The experimental results show that the proposed method can realize the direct torque control of underground belt conveyor stably and efficiently under the interference environment.