In order to study the regulation mechanisms of vegetation on rill erosion in a slope, the occurrence and development process of rill erosion with different grass spatial distributions were studied by artificial rainfall simulator and three-dimensional scanning technology. The results showed that the grass strip positioned at about 60% of the hillslope length from the top could fully exhibit its regulation effect on erosion by reducing the runoff and sediment by 7.4% and 62.9% respectively compared with bare slope. The grass strip showed direct sediment interception more than its water storage function. The regulation of vegetation on soil erosion was realized by regulating the rill formation, development and density in a slope, especially at the gully-slope. Moreover, vegetation not only changed the occurrence position of rill erosion, but also changed the erosion process and erosion pattern, the degree of erosion was greatly reduced with rill erosion transforming into sheet erosion. The information indicated that vegetation can regulate the erosion sedimentation processes by affecting the erosion pattern, and the results can be useful for better understanding the effect of vegetation configuration on rill erosion development morphology in a slope.