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 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 the increased water content, and the cohesive decreases exponentially with the increase of the freeze-thaw cycle, and the internal friction angle decreases slightly with the increase of the freeze-thaw cycle, but the fluctuation 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, which can be used to well describe the degradation law of the undisturbed loess with the freeze-thaw cycle after the test validation.