Abstract: An hydropower station is located in carbonate rock area. Where Karst strongly develops, hydrogeologic conditions are extremly complex. The Karst seepage is the key issues which restrict the construction of the hydropower station. In order to detect the distribution of groundwater and concealed karst, the authors used EH4 magnetotelluric sounding system for the survey work. And the authors had detect 10 Karst and three faults. At the end of the paper, the conclusion was put forward that the reservoir will success after the karst leakage locations be well treated.