Abstract: In view of problem that it is difficult to recover normal operation in a short time when frequency converter fails, emergency speed regulation system of coal mine moter was designed. The system uses emergency frequency conversion device to replace the failed frequency converter to control motor: when the original frequency converter fails, PLC main control unit controls emergency frequency conversion device in real time according to fault state of the motor and the frequency converter; when output of the emergency frequency conversion device reaches operating condition of the motor, switching device acts immediately, so as to realize stable control of motor speed. The simulation results show that the system can quickly access the emergency frequency conversion device when original converter fails, and has good speed regulation performance.