In this paper, the sediment motion at north passage has been analyzed on the basis of the observations of water current and sediment concentration before and after the third phase engineering of the deep waterways in Changjiang Estuary. The result shows that:the distribution of the sediment concentration of north passage in both flood and dry season appears low-high-low pattern from the upper stream to the down stream where the midstream region of north passage has the highest sediment concentration. The correlation of sediment concentration and water current averaged in a tide cycle is poor in the flood season so that the sediment advection.plays a more important role in north passage while in the dry season, the correlation is good so that the sediment suspension plays more. The main form of sediment transport in north passage is the lagrangian advection. The net sediment transport in the flood season is bigger than the dry season. The tidal pumping effect as well as the vertical-circulation effect are big in the midstream of north passage in the flood season while in the dry season, they are so small that make the water and sediment move nearly in the same direction excluding the upper stream of north passage. The reason that the tidal pumping effect as well as the vertical-circulation effect play an important roles in the midstream of north passage is that the sediment exchanging is very frequent in the midstream of north passage where there exist a high concentration of sediment flowed into north passage generated from both the mouth bar of south passage and Jiuduansha tidal shoal in a flood tide.