Abstract: Based on the geologic and hydrogeologic conditions of the upper reservoir of the Pushihe pumped-storage power station, a 3-D numerical simulation model of fractured rock was established to calculate and analyze the groundwater movement regularity of the reservoir-rock system, and the leakage volume and distribution characteristics of the flow field under various operating conditions. The groundwater system of the calculation area was conceptualized as 3-D heterogeneous anisotropic steady flow, and the permeability tensor of the fractured rock was obtained by combining water pressure test (gaining the average permeability value) and statistic method (gaining the directions of permeability tensor). The simulation results show that the total leakage volume of the upper reservoir will be 5 832.92 m~3/d under the operation condition of the normal pool level if the whole reservoir area has no anti-seepage treatment, and it will reduce by 3571.27 m~3/d after seepage prevention, which accounts for 0.22‰ of the effective storage. The results provided basis and reference for design and decision.