According to observation data and the outcomes of artificial rainfall in Wangjiaqiao basin, based on erosion mechanics mechanism, two concepts of slope erosion and basin erosion are distinguished grimly and soil erosion models of slope and small watershed have been established. The calculative products of the models manifest that slope erosion is small and equated to 7.1%~11.7% of watershed erosion. It suggests that the erosion matter of the small watershed mainly comes from channel erosion and gravitation erosion, instead of slope erosion. Therefore it is a considerable problem how to carry on works of soil and water conservation in Wangjiaqiao small watershed.