The regional floods occurring in the Three Gorges of the Yangtze River due to rainstorm have most important influence on the safety a nd operation of the Three Gorges Reservoir. For reducing the uncertainty of floo ds forecast as much as possible, a distributed hydrological model based on the c haracteristics of the catchment geomorphology has been developed to simulate reg ional floods processes. It is found that the inadequate information of rainfall from rain gauges is a dominant factor which brings about great uncertainty for f lood forecast, particularly in the mountainous area where the rainfall distribut ion greatly varies in space. The paper further tries to employ the radar rainfal l data obtained from rain gauges as the input of the model. The results of case studies in two small catchments of Three Gorges region show that the distributed hydrological model combining with radar rainfall data is a better approach to improve the accuracy of flood forecast.