Abstract: Based on the critical state soil mechanics and generalised thermodynamic theory,we constructed a constitutive model for overconsolidated clay,in which we assumed that the yield surface is tangent to the Hvorslev surface and derived an expression for the traditional thermodynamic water droplet shape parameter.The proposed constitutive model improves the weakness that the modified Cambridge model overestimates the overconsolidated clay peak strength under highly consolidated conditions.Compared with the Cam-clay model,the model requires only one additional overconsolidated clay parameter,the slope of the Hvorslev line,which can be easily determined by conventional geotechnical tests.The predictive capability of the model is well illustrated with reference to experimental data on Fujinomori clay and Shanghai soft clay.The results show that the constitutive model can reflect many characteristics of overconsolidated clay well,including stress-strain relationships,shear dilatancy,strain-hardening and softening behavior.