Abstract: After the Three Gorges dam begins its full functions, the fields of stress and dynamics of ground water in the soil and rock mass will have great changes. If other external agents such as change of water level, erosion of wind wave and rainstorm emerge, the stability of the bank slopes will be changed too. It even can cause banks to collapse. In order to research the modes of the bank collapse and the formation mechanism, this paper develops the conditions of geology and climate of the Three Gorges in a model test. Then, using the method of physical modelling and the principle of orthogonal design, this paper develops the relations and sensitivity between the pattern and width of bank collapse and factors including slope angle, water level, rainfall intensity, earthiness and wave.