A transient saturate-unsaturated water flow model is adopted to simulate the seepage field in Shuibuya Concrete Faced Rockfill Dam under different conditions: concrete face functions normally, cracks locally or does not work totally. The distribution of water head and hydraulic gradient in different dam zone is analyzed. The max hydraulic gradient that might appear in the padding zone, transition zone and main rockfill zone is suggested separately, which would control the seepage stability status of the dam. Hereby, the design standard for acceptable seepage gradient of rockfill materials is suggested. This standard can be used to estimate the rationality of hydraulic transition and seepage stability for the dam..