Abstract: Except the inlet/outlet location, anti-seepage asphalt concrete was used for the whole upper basin of Tianhuangping power station. To prevent leakage from the reservoir to the underlayer of basin, cut-off wall and curtain grouting were set. Because of the long-time effect by hydrodynamic pressure, the curtain had been weakened and reinforcing was necessary. Grouting test was made to ensure the durability of reinforcing work. The optimal grouting parameter and material were selected and used for construction.