Abstract: Soil erosion and particles loss are important factors for the development of collapse on river bank and changes in river morphology. In order to understand and predict the process of soil particles loss on river bank due to water flow, a new soil erosion test apparatus is developed that can accurately measure the quality change in soil samples in real time. Erosional tests are carried out to detect the initiation and development of erosion on a silty clay with finite thickness obtained from the bank of the Three Gorges Reservoir. A model is developed to capture the evolution of erosion and the mechanism of the erosion process. The results show that the total amount of erosion on finite thickness soils increases with time, but the erosion rate gradually decreases with time and approaches a limiting value. The rate of erosion is proportional to the void ratio, or density, of the soil and the flow velocity. The void ratio and flow velocity are incorporated in the model, reflecting the erodibility of soil and the shear forces applied on the soil's surface, which captures the evolutional process of erosion of the silty clay. The model calculates the erosion on the finite thickness soils which can be used as a reference in determining the changes in reservoir bank morphology under the action of water flow.