Combining with a project example and using the finite element method,the paper systematicly analyzed the impact of anti-seepage wall depth, blanket length and permeability of the overburden on the effect of seepage control. The computed result shows that when the permeability coefficient of overburden is relatively larger, the overburden becomes the main seepage channel and it will not achieve good anti-seepage results until the anti seepage wall inserts into the relatively impermeable layer.When the hung upside down imperious wall is used, the relative depth ratio between the anti-seepage wall and overburden is suggested as 0.7. The waterproof blanket can not effectively control seepage when the permeability coefficient of the overburden is relatively larger. The permeability of the overburden is a more sensitive factor of seepage control of dam foundation and whose size and permeability anisotropic have some impact on dam seepage field.