Abstract: By means of conventional tri-axial test of intact loess Q3 with different initial water contents and initial consolidation pressures,meanwhile based on the analysis of tri-axial test results,the stress-strain relationship characteristics of collapse loess,the variation of the strength and structural damage properties of collapse loess with the increasing of the water content and loading and the coupled effect were studied.Firstly,the stress-strain relationship and variation of structural characteristics of intact loess were investigated,pointing out the deformation and strength characteristics of collapse loess with the water content and load increasing.A new method was set up and applied to explain the change of loess structure under the tri-axial loading and moistening with the initial modulus reflecting the damage of intact structure and development of new structure under the consolidation pressure and moistening and the hyperbolie stress-strain relation reflecting the variation of structure of loess under the axial loading and moistening.