Abstract: A series of dredging and hydrologic data in situ measurement are collected to study temporal-spatial variation characteristics of siltation, and the dependency relationship of siltation on riverine discharge, tidal range and local suspended sediment concentration in the 12.5 m Deepwater Navigational Channel (DNC) in the Yangtze Estuary.The results show that: ① the quantity of siltation in DNC is much greater in flood season than that in dry season; ② the sedimentation during storms is very serious; ③ the deposited sediments mainly distribute in the South Channel—Yuanyuansha Channel and the middle reach of the North Passage; ④ the grain size of the dredged sediment in the upper reach is greater than that in the lower reach; ⑤ the quantity of siltation in the South Channel—Yuanyuansha Channel is no sensitive to the riverine discharge, but it deposits more during spring-tide and less during neap-tide; ⑥ the central position of the siltation in the North Passage varies with the intensity of discharge, when the discharge becomes small, it move up-estuary, and vice versa; the quantity of siltation in the North Passage will get greater in flood season than in dry season; ⑦ the resuspension of the deposited sediments near the estuarine turbidity maxium area is the main contribution to the siltation in the dredged navigational channel.