Abstract: A physically based distributed rainfall-runoff model was developed to simulate the hydrological processes and thus to lay foundation for soil erosion and non-point pollution study of watershed. This model discretizes watershed into a number of square elements and classifies them into hil1slope and channel ones based on the water flow properties. The runoff generation processes of precipitation, interception by vegetation and infiltration were built into the model. The generated runoff was routed using dynamic waves. The model was used to simulate the hydrological process and to model the spatial distribution of runoff depth and carrying capacity of one rainfall event after being properly calibrated and validated in Zaokou Watershed. The results showed that the runoff process could be accurately simulated and the modeled runoff depth and carrying capacity agree well with that of hydrological theory. The model provide framework for soil erosion and no-point pollution study.