Abstract: Complex stress-strain relationship is exhibited forsaturated sands under cyclic loading conditions. The large deformation andphenomena of cyclic mobility occur during liquefaction. In order to simulatethe above mechanical behaviors of sands simply and effectively, a dynamicconstitutive model which can be used to describe stress-strain relationshipfor sands under dynamic loading conditions is proposed on the basis of UHmodel for overconsolidated clay. There are three specific revisions in thispaper: (1) Ratio between the length of long axis to that of short axis forellipse yielding surface is defined as the function for slope of rotationalaxis which can be used to reflect stress-induced anisotropy. (2) Rotationalhardening rule is introduced into the proposed model to reflectstress-induced anisotropy. (3) A unified hardening parameter is establishedby coordinating rotational hardening rule and critical state behavior.Comparison between model prediction and test results demonstrates that theproposed model can be conveniently used to simulate stress-strainrelationship under dynamic loading conditions for sands. Dynamicconstitutive model is also embedded into FEM program. Stress-strainrelationship of sands for soils foundation is simulated. Simulated resultshave shown that the proposed model can be applied into geotechnicalengineering practice conveniently.