Abstract: It is complicated to accurately identify the leakage channel of diseased reservoirs in karst area because of the concealment and heterogeneity features of underground karst. Taking the Xiaohewei Reservoir in Wenshan City, Yunnan Province as an example, high power mise-a-la-masse method and audio magnetotelluric method (AMT) were used to detect the direction of leakage channel and the spatial position of leakage zone underground. The results show that: ① High power mise-a-la-masse method can accurately locate the leakage channel, and the abnormal position of multiple arc-shaped survey lines with different radii indicate the direction of leakage channel, while AMT method can ascertain the scale and depth of leakage zone. ② There are two NEE-Striking leakage channels near the contact zone of limestone and siliceous rock in the survey area, the leakage channels are formed by the long-term contact dissolution of soluble rock and non-soluble rock. The karst is well developed in the limestone of Fenshuiling formation, and the buried depth of the leakage zone can reach about 110 m. ③ Drilling and curtain grouting results confirm the reliability of the detection results. The combination of mise-a-la-masse method and AMT method can determine the direction of leakage channel and the spatial location of leakage zone, so as to guide the leakage treatment of the reservoir.