Abstract: The Hardening Soil (HS) model can only describe the behavior of strain hardening and the linear degradation of stiffness of the soil. A modified HS model was developed to consider the nonlinear degradation of stiffness. The initial backbone curve in the modified HS model was described by using segmented power function of and , and the influences of the initial static deviator stress and loading rate are also considered. The modified HS model can describe the nonlinear degradation of stiffness, the behavior of strain softening and strain hardening under different initial static deviator stress and loading rate. The modified HS model is verified against the traxial testing results for Hangzhou clay.