Abstract: The sediment in ChengBei area of Huang He subaqueous delta is studied in this article. The accumulatingand dissipating effects of excess pore water pressure along with time are considered first and the distribution curves ofexcess pore water pressure along the depth in the soil stratum are gained;the possibility of silt liquefaction is evalu-ated using the computed values and the depth of liquefaction is given. This article quantitatively analyses the dy-namic response of seafloor soil under the cyclic loading of waves and discusses the instable mechanism of soil.