Local strong permeable stratum often appear in thick overburden dam base in China's west regions. The large pore ratio and permeability coefficient adverse effect on seepage of dam foundation, and it is a problem in seepage control. This paper obtained seepage discharge and exit gradient, seepage gradient at dam heel based on seepage theory of unsaturated soil and using numerical model by Seep/w. The effects of depth, thickness, and continuity of strong permeable stratum characteristics on seepage field were studied. The results showed that seepage discharge and seepage gradient at dam heel decreased with the increased of the depth of the strong permeable stratum, when the depth of strong permeable stratum is greater than cut off wall. Instead, seepage discharge augmented as the depth of strong permeable stratum increased, seepage gradient at dam heel decreased firstly and then increased. Seepage discharge and exit gradient, seepage gradient at dam heel augmented as the thickness of strong permeable stratum increased. Seepage discharge and exit gradient augmented as open length of strong permeable stratum at upstream increased. When open length of strong permeable stratum at upstream is 50 m, which is boundary for seepage gradient at dam heel, it increased firstly and then decreased. The seepage discharge and seepage gradient at dam heel are divided by the 40 m opening length downstream, which increases first and then decreases.The escape gradient increases with the increase of opening length downstream of strong permeable layer. When the depth of cut off wall is less than 55 m, seepage parameters augmented as open length of strong permeable stratum at bottom increased. When the depth of cut off wall is between 60 and 100 m, seepage parameters increased slightly. When totally enclosed cut-off wall was adopted, seepage parameters decreased as open length of strong permeable stratum at bottom increased.