Abstract: Background Slope collapse, a serious soil erosion phenomenon in granite areas of South China, occurs mainly on mound or hill slopes under the interaction of water and gravity, causing severe destruction and threats in a wide range, including Hubei, Jiangxi, Anhui, Fujian, Guangdong, and Guangxi, mainly south to the Yangtze River, and hence a grave impact on the economy in these hilly regions. The study of liquid and plastic limits not only has beneficial for the corrosion mechanism of slope collapse, but also provides theoretic basis for the prevention and control of soil and water loss.Methods In order to explore the objective law and influencing factors of liquid and plastic limits in different soil layers, a joint investigation of field survey and indoor analysis was used to study the relationships between liquid-plastic limits and some physical and chemical properties ( such as bulk density, soil particle composition, organic matter and free iron oxides) of soil. In this study, we selected the typical granite slope collapse from the town of Wuli in Tongcheng County as the objects, taking profile samples (eluvial horizon, illuvial horizon, cambic horizon, and parent material layer), and measuring their liquid and plastic limits with liquid-plastic combine tester. The physical and chemical properties were measured using reference method. The relationship followed from correlation calculations by using SPSS. Moreover, the characteristics and influencing factors of liquid limits and plastic limits, as well as their relationships were analysed and discussed. Results The liquid limits of eluvial and illuvial horizons were both higher than 50%, while the plastic limits were about 30%. All of them are significantly higher than those of the parent material layer. We also discovered that the higher the soil clay content, organic matter content, bulk density and free iron oxides in the profile of slope collapse were, the higher the liquid limits and plastic limits were. This indicated significant positive correlation between these parameters. We noticed that the influence from soil clay content and from free iron oxides were specially remarkable (R² =0.860**,R² =0.908**). Conculsions There are the objective laws in different soil layers between the liquid and plastic limits of collapse slope. Eluvial horizon's and illuvial different soil layers between the liquid and plastic limits of collapse slope. Eluvial horizon's and illuvial horizon's liquid and plastic limits of granite collapse slope are higher. As the consequence, the original soil state is quite easy to change and thus which causes loss of soil and water, when rains wash. Furthermore, liquid and plastic limits are closely correlated with soil clay content, organic matter content, bulk density and free iron oxides. One may predict and improve the liquid and plastic limits with aids of physical and chemical properties of soil. These results provide evidences for studying the erosion mechanism and the methods of prevention of slope collapse.