Abstract: The post-liquefaction shear strain of saturated sand subjected to cyclic loading was found to be governed by the changes of the three volumetric strain components,i.e.,a component induced by the variation in the mean effective confining stress,a reversible dilatancy component and an irreversible dilatancy component.Then a new cyclic elasto-plastic constitutive model for saturated sand were established,based on the following four important aspects: ① the above-mentioned new mechanism;② a new mathematical description of the two dilatancy components;③ consistent condition that the three volumetric strain components must meet for various conditions of drainage;④ the theoretical frame of bounding surface plasticity.The model had been preliminarily confirmed to be effective through various comparisons between the calculated and tested results for Toyoura sand.It was shown that the presented model could be used well,not only to simulate the development of shear strain from a small to large range during an entire pre-and post-liquefaction process,but also to evaluate the accumulation process of large volumetric strain induced in post-liquefaction reconsolidation.The present study provided a rational and effective approach to evaluate the large liquefaction-induced deformation quantitatively.