The UHV Substations have become the key hub of the power system in China, so it is essential for the monitoring and prevention of lightning damage. We proposed a new mode of distributed transient overvoltage on-line monitoring technology, The transient overvoltage monitoring device is embedded in the design of high performance EMC outdoor cabinet and the outdoor cabinet will be placed nearby the equipment, which effectively solves the problem of signal interference and distortion caused by long distance laying signal cable. System using distributed system architecture and analysis technology, which summary the overvoltage data in each local-area network measuring point based on IEC 61850 protocol, through the backstage software we can realize the analysis of large data and analysis results, which can be used for the analysis of fault voltage and can provide effective basis to improve the equipment insulation protection level. The research results has been successfully applied in Guiyang Longshan substation and Longli substation, successfully monitored the electric overvoltage fault in the regional power grid and the fault location and fault analysis were also conducted, which verified the feasibility and practicality of the system. Research results were also installed and applied in Wuhan UHV AC Test Basement, the UHV GIS equipment switch operating overvoltage waveform were successfully collected, which verify the reliability and stability of the outdoor cabinet EMC design used in the UHV substation operation.