This paper analyzes the riverbed evolution of Chengtong reach at the Yangtze Estuary based on the measured bathymetry between 1977 and 2006, discusses the river regime evolution of Chengtong reach and the its influence on the variation of the -12.5 m deep channel from the riverbed changes in the longitudinal, lateral and vertical directions as well as the erosion and deposition change. The results show that frequent swings of local shoals in the Chengtong reach, such as Fujiangsha, Rugaoshaqun, Tongzhousha and the continuously west moving Langshansha have negative effects on the evolution of the local -12.5 m deep channel, i.e., causing some swings and even breaks. In addition, the reduced volume of sediment source due to the large-scale hydraulic engineering at upstream may cause the tendency of the increasing channel-fill volume, which is required to be further investigated in the future study.