[Objective] The impact of crop cover and management on soil erosion is usually expressed as C, which comes from the US Universal Loss Equation (USLE). It is an important factor that must be thoroughly studied for effective control of soil erosion. At present, China has a large number of models for calculating C numerically by vegetation coverage, and their relationships are various in form. However, vegetation coverage is only one of the indicators characterizing surface crop coverage, and it does not reflect any impact of field management measures on soil loss. Moreover most of the modeling methods are just based on direct regression analysis.[Method] Therefore, in this study, the crop of soybean was taken as the research object, and artificial rainfalls were simulated outdoor. A C estimation model was designed with vegetation coverage as its key factor, and plant height, crust thickness, and surface roughness as adjustment factors for zeroing approximation errors.[Result] The obtained model formula goes like:C=-0.595ln0.01V×(-0.779x₁+0.439x₂+0.061h-0.357). In the formula, V stands for vegetation coverage (%); h for plant height(cm); x₁ for crust thickness (mm); and x₂ for surface roughness (dimensionless). Of the model, R²=0.935, and the root mean square error is only 0.089.[Conclusion] The findings of this study may serve as a theoretical reference for continuous improvement of the C factor model for agricultural soil in the Loess Plateau.