Rock surface flow is ubiquitous in karst rocky desertification area exposed to bedrock,and it is easily affected by the shape of rock surface to scour soil at the rock-soil interface in the way of aggregation or dispersion,which is an important physical process of soil erosion/leakage in the karst rocky desertification area.In order to analyze the effect of rock surface flow on the soil particle distribution at rock-soil interface under different rock surface shapes,and reveal the erosion effect of rock surface flow on the soil at rock-soil interface,the fallow farmland (1-year erosion of rock surface flow) with typical rocky desertification characteristics was selected in this study,in which three typical rock surface shapes (flat,convex and concave) as the research objects.The distribution characteristics of soil particles at different horizontal distances (0~2,2~4,4~6,6~8,8~10,20 cm) and different soil layers (0—10,10—20 cm) from rock-soil interface were analyzed by laser particle size analyzer.The results showed that:(1) The influence of rock surface flow on soil erosion under different rock surface shapes is in the order:concave＞flat＞convex.The clay content of soil at the concave rock-soil interface was the lowest,and that at the convex rock-soil interface was the highest.(2) The erosion effect of rock surface flow on the soil at the rock-soil interface was mainly concentrated in the horizontal distance of 0~2 cm from the rock-soil interface.Within the range,the sand content of the soil at the concave rock-soil interface was significantly higher than that of the convex and straight type,while there was no significant difference in the distribution of soil particles at other horizontal distances from the rock-soil interface.(3) Under the influence of rock surface flow,the average fractal dimension of soil particles at rock-soil interface was in the order of convex type＞flat type＞concave type,which was proportional to the content of clay in soil and inversely proportional to the sand content.The results could provide scientific reference for further understanding the occurrence process of soil erosion/underground leakage in bedrock exposed rocky desertification areas.