Abstract: By simulating wave loads, the dynamic triaxial shear tests foundation soils of on breakwaters under isobaric consolidation and undrained flow are carried out. The analysis shows that the cyclic shear stress ratio can be fitted by the power function with failure frequency, but the fitting parameters are not constant. The pore water pressure of soils will increase continuously in the course of shear, but it does not reach the initial value of confining pressure. When it reaches the failure standard, it is about 60%~80% of the initial confining pressure. The relationship between the dynamic pore pressure ratio and the vibration frequency ratio can be well fitted by the power function, and the fitting parameters are not constant, which are related to soil properties. At the beginning, the axial strain is very small, and the compressive strain is less than the tensile strain. At the middle and later stages, the axial strain increases rapidly, and the compressive strain gradually exceeds the tensile strain.