Abstract: For understanding the issue of retrogressive erosion induced by excessive sand excavation on riverbed, including the influential factors, migration and prediction method, this paper provides a numerical model which is based on a set of equations consisted of the one dimensional Saint-Venant equation, the bed load transport equation, and the Exner equation under clear-water conditions. The MUSCL-Hancock method, a type of TVD (Total Variation Diminishing) scheme, was used to distinguish the governing equations with space-time second-order accuracy. The finite volume and finite difference methods were used separately to determine the water-flow and Exner equations to speed up computation. The model was validated by laboratory experiments which were also used to investigate the erosion process. Results show that erosion rates appear high in the early scour stage, and the retrogressive length at the early 30% time reaches to 80% of the equilibrium retrogressive length. The erosion rate increases significantly as inflow intensity, headcut height and hydraulic drop increase. The linear increasing ratio of equilibrium retrogressive length to flow discharge is 0.8 which is higher than that to height of hydraulic drop. The maximum erosion depth is approximately half of the height of headcut. Once retrogressive erosion occurs, it develops rapidly and depends on inflow intensity and height of the hydraulic drop. When considering reasonable water-sediment interactions the present model can accurately and quickly predict the erosion process.