Abstract: The zone from Changjiang Estuary Turbidity Maximum to offshore region is the main area of “source-sink transition” for fluvial sediment. It is of great significance to study the changes of regional suspended sediment concentration (SSC) and suspended sediment flux under the background of 70% fluvial sediment reduction at Datong Station. This paper analyzes the measured data based on the spring and neap tidal water and sediment observation data in the flood and dry seasons in 1982 and 2013, and mainly obtains the following insights: (1) Compared with 1982, due to the significant decrease of fluvial sediment, the vertical average SSC and the suspended sediment flux during the spring and neap tides in the dry season and the neap tides in the flood season in 2013 decreased by 40% and 25% respectively; (2) Affected by projects such as estuary waterway improvement and reclamation, the hydrodynamic conditions in local areas have been enhanced, it became an important reason for the increase of 80% and 114% in the vertical average SSC and suspended sediment flux in the North Passage and the South Passage during the spring tides in 2013 flood season; (3) The source-sink transition is manifested in the fact that in the flood season in 2013, the sediment mainly transported into the estuary from the Nanhui nearshore area increased by 101% compared with 1982, and this part of the sediment became an important part of the sediment transport cycle in the North and South Channel. The research results are of great significance for quantitatively evaluating the response of fluvial sediment reduction and local engineering in the estuary area.