Abstract: After the completion of a reservoir of Yulin in Shaanxi province, the downstream dam slope and the dam abutment of two banks appeared seepage problem. For many years, the reservoir has been operating in a bad state. In order to master the dam safety situation, the dam body typical section is analyzed by two-dimensional finite element seepage analysis through parameter inversion according to the monitoring data. The results show that the permeability coefficient of dam body filling material is large, the quality of the initial design and construction is defective, and the subsequent reinforcement measures do not meet the standard requirements. The dam body seepage line and the elevation of downstream dam slope seepage point are obviously higher than the design value. The dam seepage stability does not meet the requirements of the code.