Abstract: There exist two groundwater seepage problems for Jicun Hydraulic Power Station in recent years, i.e.,one is uplift pressure in blanket gallery to tend higher, the other is drain discharge from right no-sands tube increasing immediately when the reservoir water level reaches 54 m. Now by physical and chemical tracer and isotope tracer analysis, it is clear that the leak resistance of stub cutoff wall and impervious blanket is good on the whole, but small leaking points and a strong leakage along fault F16 in rock also exist. Drain discharge from right no-sands tube is by 74.7 percent strong leakage along fault F16 in rock and 25.3 percent reservoir water through small leak points.The strong leakage also results in the uplift pressure increasing. It is suggested that fault F16 must be treated by the impervious measure in the future.