Abstract: The loess has strongly nonlinear strength characteristics.It has different strength characteristics under different stress histories.The nonlinear strength and deformation characteristics are analyzed according to the test results.The strain-controlled undrained consolidation triaxial test is performed for the normally consolidated and over-consolidated loess.The stress-strain relationship, pore pressure-strain relationship and effective stress paths of loess are investigated based on the test results.By analyzing the experimental relationship curves of stress-strain, the secant modulus of loess is calculated.The results show that the secant modulus changes with strain and depends on confining pressure.On the other hand, the mobilized cohesion and mobilized internal friction angle are calculated.It is also shown that the cohesion and the internal friction angle change with strain.The mobilization degree of strength parameters of loess is obtained under various stress states.The evolution of strength is analyzed.It is expected to have a reference for the construction of actual projects.