The expansion of the ship lock on the existing lock hub is limited by the surrounding environment (existing lock structure,supporting facilities,houses),boundary conditions and many other factors,so the design work is more difficult.Therefore,for the second-line ship lock project of Jiantan Junction,factors such as the flow conditions of the hub,navigation conditions of the ship lock,safety of adjacent buildings and construction conditions are comprehensively considered.By adopting engineering measures such as the displacement arrangement of ship lock,the broken approach channel and the release of the berthing section,the existing structure can be avoided.The optimal lock layout scheme that meets the requirements of safe navigation and Dongjiang flood control under the design standard is proposed.It provides important technical support for the design.The layout scheme and relevant technical measures of Jiantan Junction ship lock reconstruction and expansion project can provide reference for the construction of ship lock reconstruction and expansion with complicated surrounding environment.