Abstract: This paper introduces the technical transformation and system realization of the hoister gap monitoring and protection device in Hongyang No.2 Coal Mine. Through the high-precision laser displacement sensor, we detected displacement signals, such as brake clearance, brake wear value, spring fatigue and brake disc deflection, to convert into 4-20 mA current signal to transmit to the PLC analog input port. PLC can read, analyze and convert the data in real time, and convert it into numerical value which is easy to display. Sound and light alarm signal is sent when the set value is exceeded. The practical application proves that the device has the technical characteristics of high sensitivity, strong anti-interference ability and reliable operation.