Abstract: The action of reservoir water is a key factor affecting the stability of bank slopes, in order to reveal the mechanism of bank failure of gravel soil slopes, this paper takes Baihetan reservoir area as the engineering background, and carries out the physical model test of bank failure and direct shear test of remodeled soil samples with different dry and wet cycles. The results show that: (1) When the reservoir water firstly penetrates into the soil body, then the seepage channel is formed in the slope body, the subsequent changes in the pore water pressure no longer respond with a hysteresis when the reservoir water again penetrates into the soil body. (2) When the reservoir water level rises, the middle of the slope body produces through tensile fissures and develops into a backward collapse, and the soil pressure of the slope body changes from a rising to a decreasing trend. In the stage of falling reservoir water level, the outer surface layer of the slope body shows a slip damage phenomenon due to the hydraulic gradient pointing to the outer layer. (3) The strength softening coefficient of the natural and saturated state soil samples is 70.22%. And with the increase of wet and dry cycles, the shear strength of the remodeled soil under the same positive stress shows a decreasing trend, and the angle of internal friction and cohesion also shows a decreasing trend, reflecting that the cyclic reservoir water action has a significant deterioration effect on the shear strength parameters of the soil body. The results of the study are expected to provide guidance for the evaluation of bank slope stability in Baihetan reservoir area.