Biological crust is an important type of surface cover in karst ecosystems and plays a key role in the restoration of rocky desertification and ecological control projects. It is very important to study the influence of different types of biological crust on the physical and chemical properties of subsoil under different levels of rocky desertification to explore the formation and development of soil in karst ecologically fragile areas and the stability of soil environment. In the crust layer, total nitrogen, available nitrogen, total phosphorus, available phosphorus, available k, soil organic carbon, soil field capacity and soil porosity manifest as moss crusts>mixed biocrust>lichen biocrust>algae biocrust (P<0.05), while soil bulk density manifests as algal crust>lichen crust≥mixed crust≥mossy crust (P>0.05). The physical and chemical properties of 0-5 cm and 5-10 cm soil layers on the subcutaneous surface of biological nodules are similar to those of the crust laye. biological crusts have an impact on the improvement of physical and chemical properties of the underlying soil in the latent, mild and moderate-intense rocky desertification areas, that is the moss crust and mixed crust are greater than lichen crust and algae crust and the influence of different types of biological crust on the physical and chemical properties of the underlying soil decreases with the deepening of the soil layer. Besides pH value, soil physical and chemical properties (total nitrogen, available nitrogen, available potassium, total phosphorus, available phosphorus, soil organic carbon, soil bulk density, soil field capacity, soil porosity and available potassium) of different types of BSCs are significantly correlated. Biological crust is a good prerequisite for the growth and development of vegetation as it can significantly improve the physical and chemical properties of soil, increase soil nutrient content, promote the formation of soil aggregates, enhance the bearing capacity and anti erosion capacity of land, and balance the stability of soil environment. Therefore, it is of great significance to study the mechanism of biological crust on soil physical and chemical properties improvement and the interaction mechanism between biological crust and soil environment in karst rocky desertification area for the study of biodiversity construction, material and energy cycle path, nitrogen deposition, carbon sink effect and rocky desertification control measures.