Abstract: There is a strong correlation between waterway shoal evolution and boundary shoal morphology adjustment.Combining with effects of unbalanced channel scouring and distribution, scouring and sediment supply of upper reaches, these make waterway shoal obstruction mechanism more complicated.In this study, the Luochengzhou reach in the tidal reach of Yangtze River is taken as the object.By analyzing the morphology of the shoal, the characteristics of riverbed scouring and deposition, the hydrodynamic environment and the navigation-obstructing characteristics of the central bar and beach during 1959—2021, we clarified the linkage relationship between the evolution of the central bar and beach the waterway shoal, and the scouring and sediment supply of the upstream riverbed and its influence mechanism on the evolution of the waterway shoal.Since 1981, the Yangzhong reach where the Luochengzhou reach is located has changed from siltation to continuous scouring since 1991.The scouring amount of the low-water channel from 1981 to 2021 is 3.97×10⁸ m³, accounting for 95.9% of the flood channel scouring volume; before the operation of the Three Gorges Project, the collapse of Sima bend area, the siltation of the left margin of Luochengzhou, and the undeveloped of the Sanyiqiao beach are the chief reasons for the collapse of Sima bend area.After the operation of the Three Gorges Project and before the implementation of the waterway regulation works, the decrease of sediment inflow caused the overall erosion of the shore, and the scouring of Luochengzhou provided the development space for the Sanyiqiao beach, the gradually silted Sanyiqiao beach and the runoff and sediment conditions jointly led to the development of the scouring of Luochengzhou and the right branch, that is, the change of the shape of the Sanyiqiao beach gradually changed from passive siltation to the main cause of the intertidal evolution.During 1981—2010, the sedimentation of Sanyiqiao beach, the erosion of the head and left edge of the Luochengzhou reach determined the degree of navigation obstruction of Sanyiqiao beach.Due to the riverbed scouring caused by the reduction of sediment inflow in the basin, the degree of navigation obstruction is weakened.From 2011 to 2021, the left edge boundary of the Luochengzhou is gradually stabilized and the waterway conditions in the lower shallow area are improved.At the same time, the area of the Sanyiqiao beach is changed from siltation to small scouring, and the navigation obstruction position is gradually raised to form the upper shallow area.Since the implementation of the second phase of the project, the changes in the basin inflow process conditions, Sanyiqiao beach scouring and the relative development of the right branch of Luochengzhou are still not conducive to the stability of the waterway conditions of the foreshore section of the Luochengzhou reach.It is suggested that engineering measures to stabilize the boundary of the shoal and limit the scouring development of the right branch should be taken in the subsequent improvement of the project.