Underground utility tunnels subject the surrounding loess to long-term thermal cycles. The coupled effects of temperature and moisture on the thermo-mechanical behavior of loess are investigated. A representative loess foundation pit in Chengbei District, Xining, was selected for the investigation. A site-specific warming path, simulating annual temperature variations, was applied to samples. The evolution of compressive strength, thermal conductivity, and microstructure under these dynamic thermal conditions was systematically analyzed. Results indicate that the thermal conductivity of loess decreases as temperature rises from -30 ℃ to 0 ℃, whereas an increase is observed between 0 ℃ and 60 ℃. Concurrently, significant thermal degradation of the compressive strength is observed with increasing temperature. However, the rate and pattern of this deterioration are found to vary across different temperature intervals. Thermal conductivity is governed by the combined effects of unfrozen water content and pore structure evolution. Compressive strength is primarily influenced by changes in unfrozen water. The correlation between these two properties, therefore, varies with the temperature regime. Microstructural analysis indicates that freezing induces the fragmentation of coarse particles, leading to an increase in medium-sized pores (30-40 μm) and enhanced pore connectivity. This study provides critical insights for the design and construction of utility tunnels in loess regions by realistically simulating the soil’s thermal history.