In this paper, the research work concerning the resources, structure, composition and nutritional functions of organic fertilizer,and the mechanisms of organic fertilizers in improving soil fertility and enhancing the quality of crop products, done in China since 1986 are reviewed. The relationship between the combined application of organic fertilizers with chemical fertilizers and the development of sustainable agriculture and the establishment of optimum environmental ecology are discussed. The perspective of future research on organic fertilizers should be the utilization of organic fertilizer resources as much as possible, put them into agricultural fields and let them join in the nutrients recycling in agricultural system. The cycling and re-utilization of carbon, potassium, and micronutrients would be the major research targets of cycling of organic fertilizers, so as to protect environmental quality and improve nutrient balance in food chain as well as agroecological system.