Abstract: The simulation and optimal control of water hammer in large flow and long distance water transfer projects is an important guarantee for the safe operation of water transfer projects. The special construction of surge shaft and surge tower in water transfer project may increase the project cost and construction difficulty, so it is of great significance to water hammer protection by reasonably retaining and transforming the branch tunnel to surge shaft. Taking the water transfer project of Qiandao Lake as an example, a scheme of transforming the construction branch tunnel to a surge shaft was studied, and a water hammer model for the surge shaft of inclined-branch tunnel was established. The water level fluctuation and the extreme pressure envelope of the whole line under different combinations of the construction branch tunnel were simulated by numerical simulation, and a reserving scheme of the construction branch tunnels was optimized by combining the calculation results of different branch tunnel combinations. The results showed that the water hammer pressure fluctuation of the water transfer project was well controlled by adding overflow well and branch tunnel surge shaft. The maximum transient pressure head along the line was reduced by 82.22 m, and the minimum transient pressure head was increased by 63.50 m, which could meet the safety control requirements of the project. The relevant experience can be used as reference in the reconstruction of similar engineering construction branch tunnels.