In Chinese, the word "rice field" is dung, which reflects that people have long been aware of the green circulation law of agricultural nutrients and human excrement and urine. At present, with the highly developed fertilizer industry, the return of excrement and urine to the field is still of great significance, but our existing "conventional mode" is deviated from the concept of green circulation.Two centuries ago, when the spread of running water made it possible to flush toilets, the existing systems for collecting and transporting waste were increasingly unable to cope with large volumes of waste. The best solution was to build sewers and rely on the natural flow of waste water to move the waste away. It was not until the late 1970s that people began to add nitrogen and phosphorus removal processes to the sewage treatment process, forming the current "conventional model" sewage collection and treatment system concept. From the perspective of sustainable development, under the "conventional mode", phosphorus fertilizer and potash fertilizer consumed by food production are limited non-renewable resources, while nitrogen fertilizer production consumes a lot of energy and causes air and water pollution. These elements are enriched in human excreta along with food, into sewage, into sewage treatment plants or directly discharged into water bodies.However, feces accounts for only one percent of the total domestic sewage, but contains most of the organic matter and most of the nitrogen and phosphorus in sewage. It is an important breakthrough point of "toilet revolution" to realize the green cycle of "rice field" under hygienic and comfortable conditions with modern science and technology. While popularizing sanitary and comfortable toilets, we should pay attention to the ecological significance of the toilet revolution, and divide and cure the pollution problems of toilets, sewage, livestock and poultry waste in rural areas, which will bring about the reform of human sewage discharge mode.