Scour at the foundations of hydraulic structures is a major cause of structural damage. Accurate and efficient scour prediction methods are required to guide the design and disaster prevention of structures for economic loss reduction. The traditional numerical simulation is based on the mesh method, which is not easier to converge or accompanied by large deformation of grids. This paper numerically simulated the scour process of riverbed by utilizing the Smooth Particle Hydrodynamics based on the Lagrange coordinate. It treated the sediment phase as a non-Newtonian phase and divided it into three states: sediment, bed load, and suspended load. To accurately describe the effect of liquid-sediment interaction, the Drucker-Prager and Shields stress model was introduced in the numerical model as the criteria for the transformation judgment between three states of sediment, including assigning different rheological properties for sediment particles in different states. In this study, a modification scouring algorithm based on the two-phase flow was proposed, and the sediment scouring calculation module was built and accelerated by GPU. Finally, a numerical flume model was designed for comparison with the Louvain dam-break experiment as well as the similar numerical model. The conclusions are drawn: the current numerical model proposed in this study could more accurately reflect the overall trend of scour development; the RMSE of the free surface profile of the water and sediment-liquid interface were within a reasonable range at the specified moment; the result of numerical model was in good agreement with the experimental data.