Abstract: A series of undrained cyclic triaxial tests were performed on soft clays including undisturbed and remolded samples.The transient cumulative strains under the cyclic loading with or without the initial static deviatoric stress were analyzed,and a constitutive strain model considering the cyclic stress,cycle number,OCR and initial static deviatoric stress was proposed.It was shown that the deformation of soft clay was seriously influenced by the confining pressure and the failure of soil structure.When the confining pressure was larger than the yielding pressure of the undisturbed clay,the deformation characteristics would be close to those of the remolded clay.For these two kinds of samples,there existed a turning point on strain curves under the cyclic loading,indicating failure of soil structure,and the deformation of soil before and after this structure failure should be described separately.