This paper analyzes the fault of a rheo-changing light gas false alarm. The reason of the fault is that the insulation cover of a cable of the rheo-changing body gas relay is damaged. In the case of vibration during rheo-changing operation, the humidity in the junction box increases, etc., the alarm circuit is instantly switched on through the damaged insulation cover and other common terminals, resulting in a single set of control system reporting false alarm signals. According to the characteristics of single or multiple sets of control system alarms and whether the alarm signals return, the paper analyzes whether the alarm signals are false alarms, and puts forward the operation and maintenance improvement measures of the gas relay and the disposal methods of different fault signals, so as to avoid blind shutdown of equipment after light gas alarm.