Abstract: Based on research and conclusion of the silt spectra feature and the water power of erosion in river mouth area, we analyzed remote sensing images of Taihu area showed in B1, B2 and B3 bands from China Brazil Earth Resource Satellite's CCD cameras. The results preliminarily demonstrated that there was relationship between the radius of erosion area and the speed of river inflow, and it is possible to use remote sensing method to quantitatively analyze exchange intensity of sediments in river estuary and dynamically reflect the development direction of alluvial fan. At the same time discriminatory mark for exchange intensity of sediments in remote sensing images is proposed.