Abstract: Under the environmental conditions formed by artificial flooding, the roots and stuble, which were about 15% rice biomas, as well as plenty of apuatic living things were returned into paddy soil every year, not only enriching the carbon sources but also replenishing nutrient composition in the soil. It mabe paddy soil maintain its fertility to some extent. Applying mineral fertilizer could mitigate the N. P. K. deficience caused by absorption of rice plant, and improve the nutrient level of the soil, facilitate the metabolism of rice roots and increase in amount of the root-stuble returning into soil. Applying inorganic fertilizer with the organic manure could significantly improve the physical, chemical and biological prporties of the soil. Because the paddy soils were poor in China, infarming practice, the "organo combining inorgano" application model should still be popularized, especially in returning rice straw into paddy field.