Over 20 years of sustained and rapid development after the reform and opening up has had a huge impact on the ecological environment. In 2001, less than 30% of the water in the state-controlled section of China's key river basins met the national standard Class I-III, while the proportion of inferior Class 5 water was more than 40%. Major water pollution and water ecological deterioration incidents represented by nitrobenzene pollution in the Songhua River in 2005 and the water crisis in Taihu Lake in Wuxi in 2007 occurred in a concentrated manner. The sharp decline in water environment and water ecological quality has attracted widespread attention, and the state has accelerated the construction of urban sewage treatment facilities since the "Tenth Five-Year Plan", and put forward the goals of COD emission reduction and COD and ammonia nitrogen emission reduction in the "Eleventh Five-Year Plan" and "Twelfth Five-Year Plan" respectively, and issued the "Water Pollution Prevention and Control Action Plan" in the "Thirteenth Five-Year Plan", and at the same time launched a major scientific and technological project for water pollution control, and the support for scientific and technological innovation has been significantly improved. In 2022, the proportion of class I-III water in the state-controlled section of key river basins will exceed 80%, and the water quality targets of 2030 will be achieved in key river basins such as the Yangtze River, the Yellow River, the Pearl River, the Huai River, and the Liaohe River ahead of schedule.