With the fast development of rail rapid transit, stability and deformation control of subgrade are attached much more importance,meanwhile, researches on the liquefaction and post-liquefaction characteristic of sand and sand-gravel composites come to be very significative. The saturated Nanjing fine sand and sand-gravel composites samples were liquefied under the earthquake loadings simulated by the Hollow cylinder apparatus of GDS, after that, the post-liquefaction samples were subjected to stationary loading. This research is mainly concentrated on the characteristics of stress-strain relation of the two materials. It is found that the stress-strain responses are composed of three stages, including the low intensive strength stage, the superlinear strength recovery stage and the sublinear strength recovery stage. The comparison results of the behaviour of large post-liquefaction deformation between saturated sand-gravel composites and Nanjing fine sand showed : the low intensive strength stage and the superlinear strength recovery stage of saturated sand-gravel composites are shorter while the sublinear strength recovery stage is longer. Based on the tests results, a stress-strain model was established respectively according to Nanjing fine sand and sand-gravel composites , in which the initial confining pressure and the relative density can be considered synthetically. And it was found that the predicted results by the models proposed in this paper were in good agreement with experimental datas.