Through the analysis of seepage monitoring data of Anhua reservoir dam, the anti-seepage effect of dam reinforcement project is evaluated. The analysis of monitoring data shows that the osmometer water level behind the inclined clay wall of the dam is relatively stable and has little correlation with the reservoir water level. Compared with the upstream reservoir water level, the water level of osmometer in each section falls between 7.31 and 9.30 m at high water level, which indicates that the anti-seepage effect of clay inclined core wall of dam body is better. The water head of the concrete cut-off wall in the connection section between the right dam head and the wing wall of the spillway gate is reduced by 6.65 m, and the potential difference between the front and rear of the wall is 74.7%, which indicates that the anti-seepage effect of the connection between the dam and the wing wall of the spillway gate is good. There is no obvious correlation between the water level of the pressure gauge pipe around the dam on the left bank and the water level of the reservoir, which is mainly affected by rainfall infiltration and mountain groundwater, indicating that there is no seepage around the dam.