Abstract: Under the action of cyclic loading of waves, the strength degradation of the soft clay beneath the offshore structures will take place, which will weaken the stability of the upper structure. A series of triaxial tests on silty clay of Yantai Port are carried out to investigate the strength degradation of the soft clay under different anisotropic consolidation stress ratios and different cyclic stress ratios. The behavior of post-cyclic undrained effective stress paths is also studied. Through the analysis of post-cyclic undrained effective stress paths, it is discovered that once the cyclic stress ratio is over 0.4, the trend of strength degradation of soils will accelerate, the critical effective stress ratio M will decrease and there will be some damage of the structure of the clay. The mechanism of strength degradation of clay is discussed. Furthermore, based on the equivalent super consolidation theory, a formula is proposed for the calculation of post-cyclic strength degradation of soils considering the increase of the initial effective stress induced by anisotropic consolidation. The formula is verified by the test results. Finally, through the secondary development of ABAQUS, it is applied to the numerical model of a breakwater in Yantai Port using the quasi-static method.