Abstract: In 2021, the middle and lower reaches of the Yellow River encountered rare autumn floods, during which the joint regulating operation of water projects from main channel and tributary rivers of Yellow River Basin played a key role. In the regulating process, it is a complex decision-making process to not only calculate the total flood volume, but also realize the precise connection of the main and tributary flow processes. In order to ensure the accuracy of the regulating scheme, the Yellow River Commission made great efforts to embroider and proposed the rehearsal idea of "first fine before coarse,and first tributaries before main stream", and adopted the method of real-time correction by time period, realizing scientific and fine scheduling of the Yellow River water projects. The rehearsal results show that during the autumn flood period, the average error between the water level prediction results and the measured value of Xiaolangdi Reservoir is 0.003 m, and the average error of each tributary's reservoir does not exceed 0.13 m; the average error between the flow prediction results and the measured value of Huayuankou Station is 23 m³/s, and the average error between the scheduling targets and the measured value is 32 m³/s. Results show that the fine regulating technology of the main-stream and tributary reservoirs in the middle reaches of the Yellow River has been significantly improved, which provides an important support for the flood prevention in this autumn flood.