Abstract: In the estuary reach of the Yangtze River downstream of Datong Station, the river channel is multi- branched and broad, and the flow and sediment transportation is unsteady under the interaction of runoff and tidal current. According to its characteristics, a 1-D unsteady mathematical model for suspended sediment with the channel network character is proposed to simulate the process of flow and sediment transportation in the reach from Datong to Xuliujing. Validation of the model shows that the model can simulate the scour and silting in the reach under the interaction of runoff and tidal current.