Abstract: To evaluate the stability of the large-diameter cylindrical structure in soft ground under wave loading, considering the cyclic softening effect of soft clay induced by wave loading, a nonlinear elasto-plastic constitutive model based on the concept of cyclic shear strength of clay is proposed and numerically implemented in the FEM software ABAQUS.In the model, the concept of cyclic strength is combined with the Duncan-Chang nonlinear strain-stress relationship under undrained condition.Then a series of three dimensional finite element numerical analyses are conducted to explore the cyclic capacity and failure mechanisms of large-diameter cylindrical structure in soft ground.The computed results are compared with those obtained under monotonic loading without considering the cyclic softening effect.The results indicate that the failure mode of cyclic instability and distribution of equivalent plastic strain in soft ground is somewhat different from those of ultimate failure state.Parametric studies show that the bearing capacity is reduced considerably due to the cyclic softening effect induced by wave loading with respect to ultimate bearing capacity and is influenced by some factors such as the embedment, height of load action point and cyclic loading number to failure etc.