The law of the seepage distributions and the effects of the seepage proof curtain inside the core rock filled dam, foundation and the rock of the hills on both sides of the river, the change of permeability coefficient inside the dam and its foundation and the influence of different working conditions on the seepage field are analyzed by means of finite element numerical simulation. Preliminary analysis and assessment of the seepage status inside the dam and its foundation are made with the reference of seepage stability test results and some suggestions about measures of seepage control are also put forward.