Based on the sediment test,we simulate the sedimentary situation of dredged silt and investigate the influences of different initial density of soil-water mixture and flocculant.The result shows that the initial density of mixtures has a significant impact on the deposition rate.The change of void ratio change quantity and speed,after the deposition of the void ratio and mud density is inversely proportional to the initial density.The mud deposition velocity and solution is proportional to the valence of cation.Macromolecule PAM is an effective flocculant and can make fine particles flocculate faster.