Abstract: It is difficult to accurately locate karst leakage passages due to the extremely complex hydrogeological conditions in karst regions. Field tests have verified that comprehensive geophysical methods are effective in the surveys of reservoir karst disease and its leakage passages, including the high-power mise-a-la-masse method, general mise-a-la-masse method, and self-potential method for pinpointing such seepage channels on a plane. The high-density resistivity method and cross-borehole seismic sonic perspective method can determine the depth of a karst leakage passage and its developing characteristics, providing key information for analysis of the leakage mechanism in corresponding geological conditions. In a case study of the Luotan reservoir region, our field measurements revealed three possible karst leakage passages developing in this region, via a comprehensive analysis of the survey data collected using the first three methods. And Channel No. II, a speculated karst leakage passage, was detected as the major passage of reservoir leakage. All the results had been confirmed by trace experiments. Using the data of the resistivity and sonic methods, we have detected a thrust fault, namely Fault F1 featured with broken rocks of smaller sizes on the plate of fault at the east side of this reservoir, along with a series of parallel tensional fractures Faults F2~F5. Thus, we come to a conclusion that the leakage of Luotan reservoir had a close relevance to the presence of fracture zones that had caused the development of a speculated karst leakage passage, i.e. Channel No. II, approximately along Fault F5.