Taking undisturbed loess as the research object, the effects of freeze-thaw cycles on the physical and mechanical properties of undisturbed loess were studied through plane strain tests. The results show that: as the freeze-thaw cycle increases, the surface damage of the soil sample becomes more severe; under the conditions of the same moisture content and the same consolidation confining pressure, the partial stress-axial strain of the undisturbed loess (σ1-σ3)- ε1 curve gradually decreases with the increase of the number of freeze-thaw cycles, and the degradation of the original loess (σ1-σ3) -ε1 curve by the freeze-thaw cycle increases with the increase of the water content and with the consolidation As the confining pressure increases, it decreases; according to the Mohr-Coulomb strength criterion, it is concluded that both the cohesive force and the internal friction angle show a similar linear decrease with increasing water content, and the cohesive force follows the freeze-thaw cycle The increase of the angle shows an exponential decrease, and the internal friction angle decreases slightly with the increase of the freeze-thaw cycle, but changes within 3 °. Based on the rationality of the test data, a degradation model of the undisturbed loess along with the freeze-thaw cycle is fitted. The model can be used to describe the degradation law of the undisturbed loess along with the freeze-thaw cycle.