Abstract: The seepage pressure on the base of the sluice is a very important force, which influences the stability of the sluice tremendously. When the sluice is influenced by many factors such as the water head upstream, the water head of the aquifer and the seepage lagging of clay foundation, it is very difficult to estimate the value of the seepage pressure on the sluice bottom. A series of data on Zhangshan sluice are analyzed to find the changing rules and the influential factors of the seepage pressure, which laies the base for the stability calculation.