Abstract: Periodic impounding and draining of the water reservoir would be implemented after the projects were in service.The quality of rock mass of the bank slopes would be deteriorated by "saturation-air drying" in water-rock interaction,and it would further cause great damage to the bank stability.With the impounding of Three Gorges Project,study on this problem became urgent.An experiment was performed to simulate the process of water-rock interaction on bank slopes during fluctuation of water level with sand rock as a representative of rock mass.The deteriorated shear strength of sand rock under "saturation-air drying" in water-rock interaction was determined,and might be used in the bank stability analysis.