Abstract: Since the impoundment of the Three Gorges Reservoir (TGR) in 2003, the flow-sediment characteristics of the lower Yangtze River have changed significantly. In the summer of 2020, the Yangtze River basin experienced a great basin flood second only to those of 1954 and 1998 since the founding of PRC. Based on the analysis of the flow and sediment characteristics of the lower Yangtze River since TGR operation, the characteristics of multi-year river erosion and deposition in the lower Yangtze River from Hukou to Jiangyin were analyzed, and the characteristics of riverbed erosion and deposition and riverbed evolution under the effect of the 2020 flood were discussed, using the topographic and cross-sectional data. The study showed that the average annual runoff of the lower Yangtze River had changed little since TGR was impounded, but sediment transport had decreased sharply and the relationship between flow and sediment transport had changed significantly. The Hukou-Jiangyin reach had both erosion and deposition from 1998 to 2006, and turned to unidirectional erosion in both channel and beach after 2006. After the 2020 flood, the lower Yangtze River continued and enlarged this erosion characteristic, with the erosion intensity at different water levels enlarged by 2.0 to 2.8 times comparing to the average value during 2016 to 2020. The erosion intensity of the reaches upstream of Datong was less than that of the downstream reaches. The overall pattern of diversions in the lower Yangtze River was stable. But there was a tendency for the main branch to shift in the Chengdezhou branching channel, with the right branching diversion ratio exceeding that of the left in several measurements. The anabranch developed in the Yangzhong reach, with a continuous trend of slight increase in the diversion ratio. The river was generally stable, while a number of sandbanks eroded significantly. Tonglingsha experienced shore-cutting for the first time. And avalanches occurred in some central islands in river sections such as the Yangzhong reach. The riverbed was eroded in the longitudinal direction as before, and the cross-sectional pattern of the narrower sections was further narrowed and deepened. Analysis on the evolution characteristics of river channel erosion and deposition under great flood conditions is conducive to a more comprehensive and systematic grasp of the riverbed evolution of the lower Yangtze River.