Soil erosion is a key process to alter landforms under modern geo-environmental conditions. It is also the main element to soil degradation,desertification and rocky desertification and is closely related to earth surface processes of soil,ecology and hydrology. The knowledge of climatology,geology,geomorphology,pedology,hydrology,and ecology are needed to analyze the dynamic mechanisms of soil erosion occurring and development. However,the boundaries of temporal and spatial scales need to be identified clearly. Soil erosion is closely related to soil and water conservation and they are stimulated to each other. The temporal scale of soil erosion research focuses on rainfall event,month,and year. The main topics are erosion processes of rainfall event,seasonal and inter-annual variations in soil erosion. The time scale should be less than 100 years. The spatial scale of soil erosion research should be focus on small watershed. Based on the vertical distribution of soil erosion in small watershed,site,hillslope,gully and small watershed are commonly selected to study soil erosion. Nevertheless,the contents and methods are quite different from different scales. Soil erosion includes three sub-processes of soil detachment,sediment transport and sediment deposition. The key influencing factors and the research accumulations of these sub-processes are significantly different. The studying topics change with the temporal and spatial scales. The detach-limited and transport-limited as well as their altering threshold conditions should be always remind in mind to understand your experimental results. The future studies should be enhanced on rill network and its temporal-spatial variations,sediment deposition,dynamic mechanism of gully formation and evolution,mechanism of gravity erosion development,process-based soil erosion model for small watershed.