Based on the basic fractal theory and GIS technique, the topographical fractal character of Chabagou watershed, which lies on loess plateau, is studied, the model and method that are used to calculate the fractal information dimension of the topographical fractal character of the watershed is put forward, and the fractal information dimension of the topography of Chabagou watershed is worked out. The results show that the fractal information dimension of the topography of Chabagou watershed is less than 1, and the relationship of positive correlation presents between the watershed area and the fractal information dimension of the topography. The fractal information dimension shows the quantitative character of the complex essence of watershed topography, and has provided with new solution for quantifying the macro-topography, which is one of the very important indices of the small watershed soil erosion prediction model on loess plateau.