The Dalongtan Reservoir Project is located in Jingxi County of Guangxi Autonomous Region; of which the masonry dam

is 249 meters long; it was completed and impounded in 1963. The dam foundation occurred a large number of water leakage; a number of vortex of leakage appeared; water flows under the dam into lower reaches. When emptying the reservoir

it is found that some karst collapses in the reservoir bottom. The past used conventional methods can only understand a single exploration drilling vertical direction of the geological conditions

not conducive to identify foundation for the development of horizontal and cave with broken spatial distribution. CT-between electromagnetic detection with drilling technology integration

it can make up for this deficiency. CT-between electromagnetic detection Dalongtan Reservoir dam foundation in the exploration of karst results show that this approach is feasible and effective.