In order to explore the characteristics and mechanism of soil water erosion driven by biological crust development, five coverage grades (1%~20%, 20%~40%, 40%~60%, 60%~80%, 80%~100%) were designed for the abandoned farmland plots with moss development as the dominant species in Wulongchi small watershed in Danjiangkou Reservoir area, and the bare soil was used as the control to collect samples. Soil detachment text was studied under different flow shear forces (6.12~19.64 Pa). The results showed that: The development of biocrusts significantly affected soil nutrient content, and nutrient surface aggregation was more obvious under the high coverage of crust; The development of biocrusts significantly affected the soil detachment capacity. The soil detachment capacity of bare soil was 3.58~348.95 times that of biological crust . The rill erodibility of bare soil (0.293 5 s/m) was 3.57~293.50 times that of biological crust (0.001 0~0.082 2 s/m). The relative soil detachment ability and rill erodibility decreased exponentially with the increase of crust coverage, and the crust breaking time increased exponentially with the increase of crust coverage. Nonlinear regression analysis showed that the soil detachment ability could be simulated by water flow shear force, biological crust coverage and soil bonding force (NSE=0.749). In conclusion, the development of biocrusts significantly improved soil erosion resistance. The results can provide scientific basis and theoretical reference for soil and water loss control and biocrusts management and utilization in subhumid area.