This paper proposed that the anti erodibility of soil could be described by erosion ratio(erosion depth per unit runoff depth),and could also ba used to compare the different anti-erodibilitv of soil in different areas in a same period,or in the same area in different period,in order to monitor the influence of human's effection on soil erosion,for example,arbitrarily felling of trees,afforestation and soil and water conservation.By analyzing the tendency of soil erosion in the Hunnigang watershed vve found that to describe soil erosion with erosion ratio has many advantages.