Abstract: By analyzing the behaviours of sands, a constitutive model for sands is proposed based on the UH model. The model has the following characteristics: (1) the model can describe that the isotropic compression line of sands is a curve in the e-lnp plane by introducing a compressive hardening parameter. (2) The stress ratio at the characteristic state point of loose sand is relatively large, and that of dense sand is relatively small, which can be described by the new model by introducing a dilatancy parameter. (3) The yield surface of sands is proposed by introducing a critical state parameter, and the position of the critical state line (CSL) in the e-lnp plane can be accurately described by the proposed model. Compared with the UH model, the proposed model requires three additional sand parameters which can be determined by the conventional triaxial tests. Finally, the validity of the new model is confirmed by the data from triaxial drained and undrained compression tests for sands.