Weathered granite areas are the important part of soil erosion in southeast China. In the corrupted area of weathered granite, two plots of natural slope were chosen in Tangbei small watershed. Having observed the rain capacity, rainfall intensity and the amount of soil erosion, we analyzed the three factors systematically, found the distributed law showing a curve with a double peak about the soil erosion every month in a year, and then set up a soil loss predict equation. It will present the scientific basis for the project of water conservancy, soil and water conservation and. agricultural capital construction with improvement and utilization of granite erosion in the same regions.