Abstract: This paper studies the morphological evolution and dynamic mechanics of the Jiuduansha Shoal (China), based on analysis of bathymetric data over the last 60 years (1959—2018). The results show that from 1959 to 1990, a natural evolution trend with relatively stable accretion rates occurred for the Jiuduansha Shoal particularly in the lower intertidal zone. During the last 30 years(1990—2018), the high mudflat of 0 m above the chart datum was subjected to rapid accretion due to the plant development and the construction of the Yangtze Estuary deep-water channel regulation project. During the last 20 years(1998—2018), the low mudflat 3 m below the chart datum was affected by the decrease in the river sediment supply and the adjacent large-scale water-related projects. The accretion rates slowed down and instead sediment erosion became to occur. During this period, the sediment reduction in the river basin led the slow-accretion mudflat to move upward in the Jiuduansha Shoal. In the future, the sediment supply in the river basin may keep decreasing and maintain a lower level. The low mudflat 3 m below the chart datum in the Jiuduansha Shoal will face a risk of further erosion, and the rest will be subjected to a decreasing accretion or sediment erosion.