The built Longtoushan Junction on the Ganjiang River is situated on a bend,where the upstream and downstream approach channels of the first-line ship lock on the right bank are located in the main flow area.Affected by hydro-junction operation and incomplete construction,the navigation flow conditions remain poor.The second-line ship lock is planned to be constructed on the right side of the existing first-line ship lock.Comprehensive improvements are proposed to improve the flow condition,such as reducing the porosity rate of existing partition walls and extending the length,constructing additional guide walls and berthing piers for the first-line ship lock and building new downstream revetments with complementary dredging measures.The layout scheme of the second-line ship lock is optimized comprehensively.Navigable water flow conditions for the two ship locks are validated by physical model tests under typical operating conditions involving joint operation of the power plant and dam.The results demonstrate that implementing the new wall structure can decrease the partition wall permeability low than 20%.Uniform opening patterns for sluice gates are adopted,and 20# to 24# holes adjacent to the ship locks maintain partial opening when flood discharges reach once in two years specifically.The maximum navigable discharge of the first-line ship lock can increase from 5,000 m3/s to once in five years (15,100 m3/s),while the second-line ship lock can also achieve navigation flow of once in five years.