Abstract: Based on the false alarm of the RS485 bus methane sensors in two mine, the article analyzed the install location and connection mode of the sensors, and researched the reasons of false alarm, and put forward the preventing measures. The results showed that the effective method of preventing false alarm of sensors was to reduce the series amount of bus type sensors and to shorter the busdistance, another approach of preventing false alarm of sensors caused by the sensor inner leakage is to replace the methane sensor on a regular basis and to drying process the methane sensor after up well.