Abstract: The complexity of geological conditions and the impact of climatic environment lead mountainous substations to potential geological structure safety hazards. Geological safety monitoring system for mountainous substations based on transient electromagnetic method (TEM) is very important because it may prevent the bad influence of the geological disaster to the substation and promote the development of the electric power industry in China. In this paper, the geological safety monitoring system of mountain substation based on TEM is studied. First, the mechanism of geological instability of mountain substation is analyzed. Then, the principle and feasibility of TEM are given, the technology of Geological Safety Monitoring is expounded.Finally, a mountain substation in Yunnan is taken as an example, so apparent resistivity imaging reflecting the development trend and distribution of mountain substation is obtained by TEM.The results show that it is a convenient and effective method to detect the landslide in mountainous substation by using TEM, which has certain theoretical and practical value for the site selection, research, construction and other research work.