To alleviate the problem that the water level drops more and more seriously in recent years, Jiangxi province proposes to set up regulation gates at each estuaries of Ganjiang river to raise the water level in Nanchang city during the dry season. The operation of this project will raise the upstream water level, which means the sediment transport rate will decrease and lead to deposition problems. In order to find out the deposition area and development trend, we carried out the suspended sediment deposition test on an existing physical model. The study shows that the upstream sediment is mainly deposited in the reaches near the two deltas. Some special topographic features are more likely to cause siltation, such as the wide and deep thalweg and the backflow areas at the downstream of convex banks. After the operation of the project, the erosion trend of the upper reaches of the central and southern branches will change to siltation, and the siltation of the upper reaches of the Western branch will be further strengthened. 15 years later, with the decrease of the upstream sediment intensity, the sediment siltation phenomenon will gradually move to downstream, however this will be a long process.