Abstract:【Objective】The unique “dualistic structured” (land surface and underground) hydrologic system in the karst areas of Southwest China has the areas subjected to two types of soil erosion simultaneously, i.e. surface erosion and underground erosion. Relevant researches show that soil erosions on the land surface and in the underground crevices are the two pathways for and components of the soil and water loss in the karst region. In recent years, with the intensified development in the karst region of Southwest China, construction of industrial parks and urbanization has become a hot spot. Consequently large areas of forest land and/or cultivated land have or are being stripped of topsoil for construction projects, thus depriving the land of its vegetation protection and topsoil cover, and making it completely nude and exposed to rainfall erosion. Currently, though much effort has been done studying underground soil and water loss in karst area, almost nothing has been reported about characteristics of the soil erosion on slope land with topsoil stripped of, and the researches, done or being carried on, fail to illustrate either characteristics of the spatial distribution of runoff and sediment in the surface and underground of slopes or effects of affecting factors, like rainfall, slope, underground fissure porosity, etc. of slope soil erosion on characteristics and mechanisms of runoff and sediment generation on stripped slopes in the areas. Therefore, this study is oriented to illustrate and analyze distribution characteristics of runoff and sediment in the surface and underground along stripped slopes, and further to explore effects of rainfall, slope, underground fissures, pores and holes on soil erosion. 【Method】An indoor experiment was carried out using steel troughs filled up with rocks and soil to simulate the "dualistic structure" of stripped slopes the karst area. In the experiment, troughs were adjusted to slope gradient, 10°, 15°, 20° and 25°, separately, and rainfalls different in intensity (30, 50 and 80mm h-1) were simulated on troughs of artificial slopes, different in fissure porosity (10°, 15°, 20° and 25°), to explore how the three factors affecting soil erosion on the slopes.【Result】Results show that: (1) On stripped slopes, underground erosion became more elusive and tended to be neglected when the rainfall event was low in intensity. When rainfall intensity rose up to 30 and 50 mm h-1, underground soil and water loss turned to be in dominancy and surface runoff was observed only on slopes ≥15°in gradient. With rainfall rising in intensity, underground soil and water loss varied in a curve of saddle shape, and the variation with rainfall intensity displayed an order of 80<30<50 mm h-1 in magnitude. (2) On gentle slopes,≤15°, soil and water loss occurred mainly in the fissures and pores underground, and was not observed on the surface, while on slopes, 20°or 25°ingradient, the underground sediment yield accounted for 85% ~ 97% and 59%~ 84% of the total on the slope.(3)The effect of underground holes and porosity on underground soil and water loss was significant, and a positive relationship was observed of underground runoff and runoff coefficient with underground fissure porosity. The higher the fissure porosity, the bigger the channels for soil and water loss and the more soil and water lost underground, and hence the higher the proportion of the underground soil and water loss to the total.【Conclusion】To control soil erosion in karst areas, it is not wise to pay attention only to surface soil erosion. Downwards erosion or underground soil and water loss should be the focus of attention in the karst region. In development and construction projects, it is crucial to control underground leakage, so as to avoid leakage-triggered collapse of underground karst caves. All the findings in this study are expected to be of some theoretical and practical significance to future studies on underground soil and water loss as well as guidance of soil erosion prevention and control in the karst areas.