For the safety of Daxigou Reservoir is directly related to the safty of Wulabo Reservoir downstream and Wulumuqi City, a 3-D steady seepage analysis on Daxigou Dam asphalt core well was conducted. Following conclusions were achieved： ① Fault F126 and Fault F130 pass through the foundation of asphalt core. These faults have significant impacts on the distribution of seepage field. The seepage through dam foundation and the seepage gradient under the core will be increased. Thus the erosion of the base of the core wall could be great. It is very important to control the seepage through the faults. ② Owing to the difference of permeability between grout curtain and rock foundation is not much, there is no significant effect for seepage control by extending the length of grout curtain. For the same reason, the effects of grout curtain under the core are also small. But the computation results show that the seepage field under the core wall is greatly affected by the width of the core wall.