The distribution of loess in China is concentrated in the Midwest, which is a typical structural soil. Its structure is extremely special, and its sensitivity to water is also unique. The strength and deformation characteristics of this kind of unsaturated soil have a great influence on the stress it bears. This study starts with the same stress ratio loading of loess with different moisture content and corresponding remolded loess, aiming at the changes of the structure of unsaturated soil under different stress ratios. Based on the comprehensive analysis of structural potential parameters of unsaturated soil under the condition of poor stress, the appropriate hardening parameters are constructed, and the corresponding elastic-plastic constitutive model is established. At first, the corresponding test scheme is designed, and then the test results are analyzed. Finally, the specific analysis is carried out from the constitutive model of stress elastic-plasticity of unsaturated soils.