Historical hydrologic and sedimentation data and those from recent years coastal investigations in the north part of Jiangsu coast were used in this study on the formation and evolution processes of silty coast and offshore tidal sand ridges. The result showed that the sediment discharged from the paleo-yangtze and paleo-huanghe Rivers laid the foundation of the silty coast and offshore tidal sand ridges of Jiangsu. The rapid extension of the coastline seaward and combination with pre-1855 A. D. sand banks left insufficient time for developing tidal current transport sediments, so, only the primary radial form of the tidal sand ridges (sand banks) were gradually formed. After the Huanghe River moved northward in 1855 A.D, this sediment source cut off, the influence of tidal current on Jiangsu coast sediment is strengthened. Typical radial tidal sand ridges coast and offshore tidal sand ridges are actually the new balance between hydrology and sedimentation influenced by tidal currents and waves during the period of stormy weather and their recovery.