It is one of the important features for cohesive fine sediment that there exist different transport patterns under the effect of the tidal currents. As for the Yangtze estuary, the high-concentrated mud suspension(HCMS) is driven by near-bottom flow with the range from 1 to 2 meters, to which we should pay more attention. The field investigation reveals that the generation of HCMS is related to the settlement characteristics of the cohesive fine sediment in tidal current. The effect of the HCMS movement to the back-siltation in the deepwater channel registers as the water and sediment exchange between channel and shoal. It is estimated that the HCMS transport in the transverse current may increase the amount of the back-siltation in middle of the 12.5 m deepwater channel up to 20 million ~30 milion cubic meters. This would be one of the important factors resulting in backsiltation concentrated in the middle of the north passage.