Abstract: The application process of using borehole radar technology to detect leakage hazards in a reservoir. Several main fissures in the rock of dam foundation and large water content of core wall of dam body contacting dam foundation were verified through data processing and image interpretation, thus forming the leakage conditions of reservoir dam foundation. The site with leakage problem in dam foundation was consolidated by grouting according to detection results, and finally ideal seepage control effect was obtained. Practice shows that, borehole radar, as a technical way for detecting reservoir leakage hazard, can detect the geological features such as obvious fracture planes (or holes) and the presence of high water content areas, bringing reference value for analyzing and determining the leakage site of reservoir dam.