To constraints of the existing double line ship locks on the third-line ship lock of Changsha hub,and complex boundary conditions (roads,existing ship locks,control buildings,etc.),this study conducts comprehensive comparisons including dam site selection,ship lock axis arrangement,and layout optimization.The navigation conditions at entrance areas and connecting segments are validated through experiments.By comparing straight entrance-curved exit layout with curved entrance-straight exit layout,the straight entrance-curved exit scheme is identified as optimal.It is proposed that the layout selection should integrate multiple factors:land utilization,surrounding constraints,hydraulic conditions,implementation feasibility,lock transit efficiency,interference with existing ship locks,and investment costs.The existing resources should be fully utilized in combination with the engineering practice to reduce the engineering investment and give consideration to the convenience of engineering construction and operation management.The general layout scheme and related technical measures of the ship lock have reference significance for the layout of multi-line ship locks with complex surrounding environment.