Abstract: Anti-seepage at the permanent ship lock foundation is the key part in the whole closed proof system in the Three Gorge Project. The monitoring results have shown that water level behind foundation curtain was lower than that in reservoir and has been effected less. The reduction factor of seepage pressure is less than design value. The underground water level at the two sides of mountain higher than that in reservoir matched the location topography, and has closed relationship with the rainfall. Each measuring point changed periodically.