Abstract: In the flood season of 2020, five numbered flood process occurred in the main stream of Changjiang River. The return period of flood peak and flood volume of Cuntan station in the upper reaches of the Yangtze River after reduction calculation reached 100 years, more than the flood in July 1981. The Changjiang Water Recources Commission strengthened monitoring and early warning, planned the flood control needs of mainstream and tributaries, upstream and downstream, left and right banks as a whole, gave full play to the role of reservoir groups in flood control and peak shaving, and scientifically and orderly implemented joint operation of water conservancy projects such as reservoir groups, breach of polder embankments and drainage pumping stations. In this paper, the operation system of water conservancy projects in the Changjiang River Basin and the flood control operation objectives of reservoir groups were systematically introduced. Combined with the practice of water conservancy projects operation in 2020, the effectiveness was analyzed, and the practical problems in the operation were considered. Through the implementation of joint operation of water conservancy projects, the flood peak water level of Sichuan-Chongqing reach of the Changjiang River mainstream was reduced by 2.9 to 3.3 m, and the maximum water level of Yichang-Datong reach of the middle and lower reaches was reduced by 0.3 to 3.6 m, which avoided exceeding the guaranteed water level of Yichang-Shishou reach and shortened the warning time of each station of the middle and lower reaches by 8 to 22 days. The application of the above water conservancy projects operation measures brought a huge benefit for flood control and disaster reduction. After the flood test in Changjiang River Basin in 2020, it was deeply realized that on the basis of in-depth study, using hydrometeorological forecast in real-time water conservancy projects operation can better benefit in flood control and disaster reduction. It was proposed that new technologies such as artificial intelligence, machine learning and big data should be introduced in the future. Mechanism model and data-driven model should be combined to break through the bottleneck of traditional forecasting and operation technology. It is of great significance to build a comprehensive operation support system for controlled water conservancy projects in the Changjiang River Basin based on the whole basin simulation, improve the forecasting and operation ability, and provide support and guarantee for the construction of peace Yangtze River.