Abstract: With special considerition on the conservation of mass, the effect of sediment deposition and entrainment on the water continuity is reflected in a numerical model.A simple method was used to apply for the frequent variation of water boundary conditions in high sediment laden flow river.A mixed method was employed to solve the numerical equations of water and sediment movement, and finally, a special flood process in the Lower Yellow River was calculated with the model to verify the applicability for the high-sediment laden flow river.