Abstract: To evaluate the seepage-proof efficiency of the Hongping pumped storage power station, this paper presents an analytical method which integrates the secondary subdivision technology of drain holes and the modified node virtual flow method based on a whole model of the dam basin and underground power house. This model uses the secondary subdivision to simulate complex seepage control measures, such as densely distributed drainage holes, and calculates the exact solution at frozen points by considering the contribution of given nodes to the flow of transition elements. It adopts the method of enlarging transitional zone to determine the location of seepage free surface. Thus, this analytical method offers a convenient and accurate tool for the seepage problems with complicated seepage-control measures. This paper also discusses a technique of specifying groundwater boundary, which is useful for seepage control optimization of similar projects.