Abstract: There are many engineering problems at silty coast areas in the Bohai Sea,such as the formation of collapse depressions at the Yellow River subaqueous delta, the breaks of marine cables at the Chengdao sea area, the drastic sand siltation of the open channel of Huanghua harbor, and the sand siltation of the Dongying harbor experimental channel. Based on the cause analysis of these problems and the dynamic characteristics of silty soil under storm waves, we propose that the strength of silty seabed deceases while it is approaching liquefaction due to storm waves, and the seabed is sheared and oscillated under waves, resulting in drastic increase of the mobile sediment. As a result, the influence of engineering geology characteristics of silty soil should be taken into account when we research the problems of sediment movement of silty coast areas.