Abstract: Based on a model for 5 typical sequences of silt seabed in Chengdao sea area in subaqueous Yellow River Delta and the Biot's theory, numerical simulation in the 10 m deep-range is done to calculate the stress field, displacement field and excess pore water pressure of seabed. The calculated results are compared with the actual observed ones. This study reveals that under the wave loads, the displacement and the pore water pressure of the multi-layer seabed have the first extreme value in surface silty layer, then comes the second extreme value in the next “weak” layer, and stress will be reduced sharply at the interface position. The first extreme value is the dynamic factor for small geological disasters in the surface layer, and the second extreme value directly leads to large-scale geological disasters. The sedimentation sequences play a key role in the stability of the seabed, and the “upper hard-lower soft” structure is most unstable, where large-scale geological disasters will happen after strong wave action.