In the investigation of leakage in Sanmentou Section of Main Channel of Yanshiling Reservoir， as the channel is located in the karst development area， the multi-dimensional method of parallel electricity method was combined with geological radar to study the causes and distribution range of hidden defects.Based on analyze the feasibility of the integrated geophysical exploration technology，using the method of parallel electricity， considerable geoelectric data volume was collected rapidly to support 2D dam leakage detection and survey hidden defects of channel bottom. In combination with radar imaging， development characteristics of karst caves was identified effectively. Practical application demonstrates that 2D resistivity images of different elevations reflecte the scopes and depths of potential hazardous dam areas of leakage and spatial connectivity of potential hazardous areas；3D results obtained by the method of parallel electricity reveal three-dimensional structure of karst caves on the bottom of the channel and avoid complex problems of conventional pseudo-3D electrical layout. In addition， geological radar can identify the scope of karst development effectively. Comprehensive results of detection show that dam leakage in the Sanmentou Section is mainly related to its concealed filling karst caves； and there are tunnels connecting upstream and downstream caves. Further case studies show that the multi-dimensional imaging technology of parallel electricity and geological radar have a high precision of location with dam leakage in the karst area， thus providing a basis for objectives-oriented dam governance.