Based on the reciprocating water in the estuary, the flow structure restricts directly the distribution of suspended sediment with its changing in the process of rising and falling. By using the ECOMSED model to simulate the dynamic processes of flow and suspended sediment in the Yangtze estuary, the paper reveals the variation of the distribution of suspended sediment during the flow movement. The results show that the concentration of suspended sediment (C_SS) is mainly effected by the actions of runoff and tide in the Yangtze estuary. With the increasing of the discharge and the tidal range, the C_SS has an increasing tread, the east boundary of the high C_SS range is gradually expanding, and the area is also constantly expanding by the increasing amplitude generally decreasing. The average boundary of the high C_SS area in ebb process is 0.06‰ larger than it in rising process. The high C_SS area has a retreating phenomenon in the rising tidal process.