Soil erosion reduces the effective water available to plant, and loses the soil nutrient material with the soil fertility structure destroyed, effecting the farm tillage system. So, the soil productivity is cut down to a great extent. Erosion-Productivity Impact Calculators (EPIC) quantify the relationship systematically between soil erosion and soil productivity. The models involve 9 factors, that is, hydrology, meteorology, water erosion and wind erosion, the state of nitrogen and phosphorus, soil temperature, crop growth, tillage and treatment of crop residue, economic factors, and irrigation-drainage of soil as well as fertilization, etc. They are expressed with 36 equations. To protect and raise the soil productivity, we should develop and enhance this research in order to formulate EPIC with distinguishing Chinese feature.