Abstract: Coal mine safety monitoring systems mostly use CAN bus-based multi-master communication mechanism or RS485 bus-based master-slave communication mechanism, which calculates the power-off time by intercepting the time of methane overrun messages and the time of power-off messages of the breaker. Since the communication mechanism and communication protocol of the monitoring system of different manufacturers are different, it is impossible to design a unified gas locking detection method and device. At present, there are many researches for shortening the power-off time of gas electric locking, but there are few researches on gas electric locking detection. In order to solve the above problems, a gas electric locking detection device for safety monitoring system is designed based on the detection method of sensor communication switching and analog sensor message sending. The sensor communication switching method is not limited by the communication protocol and bus form, and the same manufacturer's sensors, substations, circuit breakers and safety monitoring software are used for detection, without the need to know the communication protocol. This method is simple to operate and does not require the cooperation of the manufacturer. It is suitable for gas electric locking detection using the master-slave communication mechanism. The analog sensor message sending method uses the detection device to simulate a methane sensor to send messages to communicate with the substation. There is no need to know the communication protocol or consider the communication mechanism. The messages are provided by the manufacturer and configured according to the order and times of message sending. This method is more cumbersome to operate and requires the manufacturer to provide communication messages. However, the test accuracy is higher and the method is suitable for gas electric locking detection of various communication protocols. The verification results show that the sensor communication switching method is not suitable for CAN bus-based multi-master communication mechanism. The analog message sending method based on RS485 or CAN bus can achieve local power-off time less than 2 s and remote power-off time less than 20 s. The timing accuracy of the two detection methods can both reach 0.01 s.