Abstract: In order to solve the problems such as the lack of real-time data of the mechanical characteristics of the high voltage switch operating mechanism and the unclear state of the mechanism, the paper proposes an on-line monitoring method and system of the operating mechanism based on the giant magneto resistance effect sensor. By means of installing the giant magneto resistance angle position sensor at the shaft end of the transmission shaft of the mechanism and deploying the monitoring and diagnostics terminal in the station, and the key parameters such as the current, angle position and contact current of the closing/opening winding of the operating mechanism are monitored. The wave recording function is configured in the monitoring and diagnostics terminal to form the common format for transient data exchange recording files. The files are sent to the regional operation and inspection cloud platform through the Internet of things, and compared with the current and contact travel strokes of the operating mechanism during normal opening and closing. The status and fault causes of the operating mechanism are analyzed through the above methods. The system assesses the operating status of the operating mechanism, analyses the causes of faults and supports the use of mobile terminals to view the status of the operating mechanism in real time.The monitoring function of the switch-operating mechanism is applied in the online monitoring of circuit breakers, and the application results show that the online monitoring can well detect abnormalities in the operating mechanism, which plays an important role in reducing the failure rate of switchgear.