In order to further explore the failure mechanism of canal slope, triaxial tests and scanning electron microscope (SEM) tests were conducted on expansive soil in northern Xinjiang under dry-wet-freeze-thaw cycle conditions,the physical deterioration mechanism of expansive soil was studied from macroscopic, mesoscopic and microscopic perspectives,and the influence of dry-wet-fueeze-thaw cycles on the parameters of the Duncan-Zhang E-B model was analyzed. The results show that under the dry-wet-freeze-thaw cycle conditions, the stress-strain curve of the expansive soil exhibits a hardening type, and the volumetric strain curve shows shear shrinkage characteristics.The cohesion decreases nonlinearly with the increase of the number of cycles, with the most significant reduction occurring during the first cycle, and it tends to be stable after seven cycles. The internal friction angle changes little and remains almost constant.During the cyclic process, cracks in the expansive soil develop from both ends to the center, the internal crack grids gradually converge and form a crack core in the weak area of the soil body, and the overall failure surface gradually develops from an initial “Y” shape or “X” shape to a “claw-shaped” longitudinal penetration damage surface. The cyclic action caused the aggregated structure of the soil to break down and reorganize into a loose flocculent structure, the intergranular pores increase, and the clay particles gradually peel off and detach, resulting in the structural damage of the soil body. The weakening of the intergranular bonding effect is the main reason for the decrease in cohesion.The cyclic action has significant influence on the Duncan-Zhang E-B model parameters n , K , and K b. When the number of cycles is more than three, the changes in these parameters are relatively small. Exponential function fitting indicates a good correlation between these parameters and the number of cycles.