Abstract: In order to improve the utilization rate of surface water in small watersheds and solve the problem of irrigation water in mountainous areas, We have carried out the technical research of anti-seepage modification of Juershang silt dam in Pianguan County, Shanxi Province. Aiming at the upstream slope of the silt dam, five reconstruction schemes were put forward including original soil thickening, clay inclined wall and composite geomembrane. The seepage and slope stability of the original dam and various modification schemes were numerically simulated considering the coupling effects of seepage field and stress field. The results show that the original dam is greatly affected by the seepage water and cannot store water safely; only the original soil thickening of the upstream slope of the dam cannot make the dam meet the requirements for seepage prevention; laying a clay inclined wall or geomembrane anti-seepage body on the upstream slope can effectively reduce the infiltration line and the seepage flow, and improve the stability of the downstream slope of dam; the geomembrane scheme has better safety and feasibility than other schemes, and can be given priority if conditions permit. The research results have certain guiding significance for the anti-seepage transformation projects of similar silt dams.