Abstract: For the first time, a series of simulated experiments on normalized integrated model for different degrees of erosion control were conducted to investigate the relation of runoff and sedimentation. The results showed that there is a critical value for the erosion control of slope surface, which was about 80 percent, in accordance with the experimental results, in the secondary sub regions of Hilly and Gully Leoss Regions. Moreover, the density of dams in the gullies had obvious effects on runoff and sedimentation in watersheds. And the critical value for dam density on different degrees of erosion control was suggested for the secondary sub regions.