A mathematical model is employed to predict and analyze the effectiveness and impacts of the Phase II Project of the South Passage Channel Regulation in the Yangtze Estuary.The results indicate that,after the project implementation,the ebb current velocities significantly increase along the south side of the spur dike and in the main channel of the bar area,providing critical hydrodynamic support for dredging the shallow section of the bar and maintaining an 8-meter-deep main channel.The spur dike reduces tidal dynamics in the Jiangya North Passage to the north,forming a sheltered area that effectively stabilizes the hydrodynamic boundaries of the South Passage and the Jiuduansha Wetland.Following the project,the channel morphology in the bar area becomes more stable,with enhancing flow dynamics in the main channel,promoting scouring,and a stabilized thalweg—collectively improving channel stability and facilitating construction and maintenance.The results validate the correctness and feasibility of the regulation strategy focusing on “nourishing shoals,stabilizing channels,guiding flow,and blocking sediment.” Moreover,the project shows negligible impacts on adjacent hydraulic structures and the North Passage deepwater channel,with minimal influence on the South Harbor,the South Passage coast,major hydrological facilities,and floodgates.