It is difficult to calculate the axial strain of saturated soft clay subjected to long term cyclic loading by using traditional explicit or implicit model. On the base of total stress model of consolidated-undrained shear model of saturated soft clay and considering the shakedown character of clay under small dynamic stress ratio, a shakedown model is set up to calculate the axial accumulative plastic strain. The proposed shakedown model can effectively descript the character of saturated clay displacement under cyclic loading. Because of using the equivalent method, the step of numerical integration can be chosen arbitrarily. The large numbers of calculation can be reduced, so calculation time will be saved considerably.