Abstract: Non-point source pollutants are mainly carried over land and into stream networks by surface runoff, and how to simulate surface runoff is the key to determine the loads of non-point source pollutants. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use of the watershed. Five subwatersheds that can represent the whole watershed are chosen and their average annual precipitation, average annual surface runoff and percent land use are calculated respectively in digital Wujiang watershed based on climatic and hydrological data from 1956 to 2000 and land use data of 2000. The surface runoff is assumed to be a function of precipitation and land use and the regression tool is used to determine the relationship between surface runoff, precipitation and percent land use. So the rainfall-runoff models in all kinds of land use types are built. The result shows that the relative errors are all below 7% and the accuracy of the models is high.