In order to simulate truly the underground water seeppage of Jiangkou Hydroelectric Station's dam area, the threedimensional seepage model was founded by 3D FEM under the conditions of the features of terrane anisotropism and supplementary boundaries of rainfall infiltration. The dam area is separated into several zones according to penetrability in horizontal and vertical directions. A series of models is considered. The results of these models show that the seepage control of proof curtain and draining system is efficient, and the data may be used as the basis for design.