Abstract: A modified direct shear stress instrument is employed to study wet shear evolution of saturated loess under different levels of shear stress. The wet shear evolution rules of undisturbed and disturbed loess are further discussed under different humidifying water volumes according to a certain level of shear stress. On such a basis, a structural parameter of loess mω is defined. The results show that during the wetting process of loess, the curves of shear displacement over time can be divided into two stages: rapid development stage and stability shear stage. The shear stress has small impact on the shear strength of the saturated loess samples, and the vertical deformation is mainly the collapsible one. The structural parameter exhibits strong sensitivity to water under low consolidation pressure and low water content, and weak sensitivity to water under high consolidation pressure and high water content.