Abstract: After the Yellow River returned to the north, the sources of the sediments in the northern part of the radiant sand ridge area in the South Yellow Sea have been lacking. As a result, the evolution pattern of the radiant sandbar area is bound to change. Based on the nautical charts of different periods in the radiant sand ridge area, and combining with the large scale underwater topographic data of typical areas obtained in winter ana summer and the grain-size analysis of sediment samples, the spatiotemporal variation characteristics of seabed scouring and siltation in the northern part of the radiant sand ridge area in the South Yellow Sea and the scour risk of pile foundation and submarine cable of offshore wind power plant are analyzed. The results indicate that the Xiyang Deep Trough on the west side of the radiant sand ridge area expands toward the south side and the east and west sides and is still deepened and adjusted constantly by scouring under the action of tidal currents. The Xiaojia Trough, the Xiaobei Trough, the Dabei Trough, the Chenjiawu Trough and the underwater sand ridges between the deep troughs are all swing markedly and have a trend to move westward as a whole. The Liangyue sand ridge, the Taiping sand ridge and the Niluoheng sand ridge are in a scattered distrtibution. The change and disappearance of these ridges indicate that the changes in terrain of the area are active under the action of tidal dynamics. In the typical areas, the changes of terrain in the areas of sand ridges and deep troughs range from −0.5 m to 1.4 m in winter and summer of a year. The sand ridges also tend to migrate toward the steep slope located on the west side. According to the analysis, there are three areas currently in a scouring state in the northern part of the radiant sand ridge area in the South Yellow Sea. This will have a certain impact on the safety of pile foundation and submarine cable of offshore wind farm.