Abstract: In order to determine what kind of hydrodynamic erosion factors can describe the runoff detaching soil process more accurately, soil hydrodynamic erosion process was simulated systemically by runoff scouring experiment in a flume with the gradient of the slope ranging from 3° to 30° and the flow discharge from 2.5 to 6.5 L/min. And at the same time, nearness degrees between the hydrodynamic erosion factors, including flow energy consumption per unit width, flow shear stress, stream power, unit stream power, and soil detachment rate were calculated and analyzed by applying the theory of fuzzy nearness degree. Results show that the nearness degree between flow energy consumption per unit width and soil detachment rate is the highest and the relationships between them are linear when the flow discharges are the same. And the nearness degree between stream power and soil detachment rate is the second highest and the relationship between them is also linear. The research shows that the runoff detaching soil process can be described more accurately by the factors of flow energy consumption per unit width and stream power.