Abstract: To meet the demand of various industries for high-resolution and high-precision precipitation data, this study establishes the downscaling models of the TRMM precipitation data of the Xiangjiang River basin based on the methods of multivariate linear regression (MLR) and geographically weighted regression (GWR). The leave-one-out cross-validation method was adopted to select the optimal model, and a satellite-ground fusion precipitation product with a resolution of 0.05° was obtained through inversion. On this basis, the spatial-temporal change characteristics of the precipitation in the Xiangjiang River basin were analyzed. The results are as follows. The spatial resolution of the TRMM precipitation data was greatly improved after downscaling. As verified using the precipitation observed at meteorological stations, the coefficient of determination of the TRMM precipitation data increased by more than 0.27, and the root mean square error and average relative error of the TRMM precipitation data decreased by more than 28.42 mm and 29.88 percentage points, respectively on average after downscaling. All these indicate that the regression downscaling model that takes account of vegetation, terrain, and geographic elements can accurately describe the spatial distribution characteristics of precipitation. According to the verification using the precipitation observed at meteorological stations, the coefficient of determination of the GWR downscaling model increased by 0.06 compared to the MLR downscaling model. Meanwhile, the root mean square error and average relative error of the precipitation data obtained using the GWR downscaling model decreased by 14.88 mm and 8.83 percentage points, respectively on average compared to precipitation data obtained using the MLR downscaling model. These indicate better effects of the GWR downscaling model. The spatial-temporal change characteristics of the precipitation in the Xiangjiang River basin during 2006—2017 are greatly different on different time scales, which is reflected in the changing trend and its significance and the locations and area of corresponding zones.