Abstract: The structure of natural clay will tend to be damaged under the external load, and its mechanical characteristics will change, especially under the condition of dynamic load. The mechanical change of Tianjin marine deposited structured soft soils subjected to cyclic loading is investigated. The resonant column tests and post-cyclic monotonic tests on the soft soils which experience different cyclic loadings are performed. The resonant column test results show that the degradation rate of stiffness is from quick to slow with the development of structural damage. The revelation of the strength degradation law is similar to that of the stiffness degradation law. This degradation law is analyzed from the structural damage view, and the ratio of stiffness to strength of soft soils under the damage process is discussed. A conclusion is dram that the degradation degree of stiffness is larger than that of strength.