Abstract: As the core node of the "belt and road" Central Asia land route, the engineering geological stability of Ili region in Xinjiang is crucial to regional development. The mechanical properties of Quaternary loess, which is widely distributed in the region, are continuously deteriorated under the complex climatic conditions such as seasonal freeze-thaw, dry wet cycle, heavy rainfall and the continuous effect of engineering activities, thus inducing frequent regional loess landslides. Therefore, it is of practical significance to further study the effect of freeze-thaw-wetting-drying (FTWD) cycle on the mechanical properties and nonlinear degradation law of Ili remolded loess. Based on the consolidated undrained triaxial shear test and microscopic test under FTWD cycle, the stress-strain response, strength parameter evolution and damage mechanism were revealed from the macro and micro scale. On this basis, assuming that the micro element strength of loess obeys the Log-logistic distribution function, the damage model of loess is established and its applicability is verified. The results showed that the shear strength decreased by 22.9% with the increase of the number of cycles, and the cohesion attenuation (45.2%) was significantly higher than the internal friction angle (7.27%). In the microscopic image, it can be seen that the compacted loess presents the characteristics of aggregate structure.The deviatoric stress-strain relationship curve of Ili loess sample is mainly strain hardening type. The cohesion of Ili loess decreases significantly with the increase of FTWD cycles, while the internal friction angle changes slightly. Combining the traditional Duncan-Chang model with the statistical damage theory, a constitutive model which can uniformly characterize the strain hardening and strain softening characteristics under different FTWD cycles is established, and the model parameters are solved. The model verification shows that it has good predictability for the test results under different confining pressures and cycles.