Abstract: According to the theory of sediment transport mechanics, it is assumed that the movement of the soil particle on the sloping land depended on the effective shear stress of the flow which is the difference between the shear stress of the flow and the criticle shear stress of the particle on the sloping land. Therefor, a calculation formula of the soil, erosion on sloping land is deduced. And a model of the sediment yield from watershed is developed by using the soil erosion formula obtained. The new model has more physical basis of soil erosion and transport and can be used to predict the sediment yield in a flood period or in a year with less parameter which can be obtained based on the historic data. The model is verified with measured data of the Pei Jiamao catchment in the North Shanxi Province and the results are satisfactory.