Rock surface flow (RSF) is a form of runoff resulting from the secondary redistribution of natural precipitation across exposed bedrock outcrops in karst regions. The RSF can scour the limited soils around the exposed bedrock outcrops from the surface and subsurface. However, it is still unclear what changes will occur in the multi-path runoff erosion process of complex rock-soil structures under the scouring of RSF. To address this problem, this study invented a simulated rock-soil structure device where the RSF enters the soil at an angle to scour the soils at the surface and rock-soil interface (RSI), simulating the scouring erosion driven by the RSF. Hence, a series of RSF scouring experiments on undisturbed soil at the RSI, collected from around outcrops in a representative rocky desertification control plot in a typical karst area of China, were conducted. Results demonstrate that the RSF primarily transforms into RSI flow and underground pore (UG) flow, with the flow volume ranked as UG > RSI > surface. This runoff transformation facilitates substantial subsurface soil loss, with RSI and UG flows contributing 44.4 % and 44.1 % of the total soil loss, respectively. The RSI and UG flows are the primary mechanisms driving subsurface soil leakage, with the RSI acting as a key conduit for stable soil loss. Sediment yield from the RSI showed a significant positive linear correlation with runoff yield (p < 0.05). The RSF flow volume (RSFfv) was significantly (p < 0.05) positively correlated with sediment yield across surface, RSI, and UG pathways, while the inclination of the rock surface (IRS) showed a non-significant positive trend. These findings provide novel insights into soil erosion processes on rocky desertification slopes with extensive outcrops. Incorporating RSF-induced erosion into predictive soil erosion models will improve their accuracy and reliability in karst rocky desertification (KRD) areas.