The fractal dimension measure of watershed topography is the unsubstantial part of topography fractal study,and it is very important for the prediction model of soil and water loss in small watershed.Based on the principle of measuring the fractal box dimension and the character of watershed topography,the approach for measuring the fractal dimension of watershed topography is put forward by the technique of GIS,whose data is from contour line. We operated demonstration research by taking Chabagou watershed as an example.The results show that this approach is fast,exact,credible and can get the fractal box dimension of watershed topography of different scope.