Abstract: Abstract: Soil surface microrelief plays an important role on the soil erosion processes like runoff, infiltration, soil sealing and sediment transport. However, there is relatively little study on the soil surface microrelief in soil erosion process and those studies are mostly conducted in the Loess Plateau in China. The purpose of this study was to study the feasibility of applying the Instantaneous-Profile Laser Scanner imported from the USA to determine the features and law of soil surface microrelief evolution in red soil region of Southern China. In this study, three soils derived from Quaternary red clay and Shale widely distributed in red soil region were selected, and the changes of soil surface microrelief during rainfall were studied in three intermittent rainfall events by using the Instantaneous-Profile Laser Scanner. With both its positional accuracy and elevational accuracy amounting to 0.5 mm, the Instantaneous-Profile Laser Scanner has been widely applied to the soil erosion process, soil physical property, statistical analysis of geography and topography etc. In the study, soil surface roughness obtained from the scanned image illustrated the changing process caused by the rainfall and runoff. The results showed that: 1) With the intermittent rainfall continuing, the soil surface roughness decreased, resulting from the combined effect of the detachment of raindrop and the transport of runoff; After the third rainfall event, the surface roughness of soil derived from Shale, soil 1 derived from Quaternary red clay, and soil 2 derived from Quaternary red clay decreased 18.2%, 18.4% and 11.8% respectively; and 2) For all three soils, the greatest decrease of soil surface roughness was found in the first rainfall event, which differed from the other two rainfall events significantly. Specifically, the decreases of the surface roughness of soil derived from Shale (16.1%) and soil 1 derived from Quaternary red clay (19.7%) were much higher than that of soil 2 derived from Quaternary red clay (9.6%) for a higher aggregate water stability compared with the other two soils. For all three soils, in the first rainfall event, most aggregates were broken and soil crust began to form because of rainfall splash leading a sharp decrease of soil surface roughness. In the second and third rainfall event, the decreases of soil surface roughness event were not obvious for soil derived from Shale and soil 2 derived from Quaternary red clay. The crust formed on the soil 1 derived from Quaternary red clay during the third rainfall was prone to be destroyed due to its own unstable soil structure, leading to the increase of its roughness of soil surface. The application of submillimeter-level high-precision laser scanning and computer digital image processing method is in favor of researching quantitatively the characteristics and laws of soil surface microrelief changes during the process of water erosion on hillslope. Meanwhile, this paper throws a light on the study of the soil surface microrelief by discussing its status quo, directions and significance during the water erosion on hillslope.