Quantifying topographic feature of watershed synthetically and scientifically is one of key problems forwatershed soil erosion prediction model that is used everywhere.Fractal theory has provided new solution for study on quantifying topographic feature of watershed.Based on fractal theory and the general model of small watershed quantitative coupling relationship between topographic fractal feature and sediment yield was studied by simulation rainfall experiment

high precise photogrammetry and GIS technology.The results showed that the process of soil erosion and sediment yield of watershed model took on phase characteristic with early phase

active phase and stable phase according to relative sediment transport rate

which avoided the influence of rainfall characteristic on soil erosion and sediment yield process of watershed model.During the different phase

the variation trend of fractal information dimension (D_i) of watershed model topographic feature was similar to that of relative sediment transport rate(S_r) of watershed model

which took on rising firstly

then falling down and becoming stable.Relative sediment transport rate (S_r) of watershed model and the fractal information dimension(D_i) presented positive correlation with power function.The correlation exponent r~2 was 0.742 3.Fractal information dimension(D_i) of topographic feature of watershed model has perfectly described the influence of topographic feature on soil erosion and sediment yield process of watershed model

and it can be as the integrated index of quantifying topographic feature for soil erosion and sediment yield prediction of watershed model.