Some existing state-dependent mathematic models for compression curve of cohesionless soils are described and analyzed briefly. Isotropic compression tests on sand with different initial densities are performed. On basis of the results

a new state-dependent stress-strain model for cohesionless soil under hydrostatic compression is proposed. The model is able to describe well stress-strain behaviour which develops throughout first loading and can be adaptable to different freshly deposited cohesionless soils subjected to isotropic compression over a wide range of stresses and densities. The model parameters can be determined simply and conveniently from isotropic compression test. Comparison with experimental data of four types of sands indicates that the model can gives excellent predictions to the measured isotropic compressive behaviour; and it can be used to construct generalized state-dependent constitutive models.