The seepage of the reservoir is one of the key problems in hydroelectric project. A great deal of seepage could cause the reservoir water recharge may not up to the designed level and then influence the engineering effect. The osmosis from the seepage could cause the depravation and penetrating damage of the dam base, and influence the safety of the dam. Finite difference method is used to estimate the seepage of the reservoir, calculate the seepage volume, optimize the best blanket length and calculate hydraulic gradient of the dam base. Because the seepage volume.and the hydraulic gradient are very large, many measures such as blanket, loaded filter, etc. are suggested in the paper, to offer the referense for designing and decision.