The active layer thickness (ALT) is a critical indicator of permafrost response to climate change, holding important implications for ecological and hydrological systems. This study analyzed ALT trends and assessed dominant influencing factors along the Qinghai-Tibet Highway from 2004 to 2023, using observational data from 9 sites. Results showed a warming trend of 0.25 degrees C/10 a across the study sites, with an average ALT increase of 64.7 cm (2.84 cm/a). The surface energy budget, particularly the annual global radiation accumulation and net longwave radiation, was identified as the predominant factor influencing ALT changes. Although soil moisture and vegetation cover did not show significant correlations with ALT across all sites, a significant negative correlation was observed when analyzed by underlying surface type, with alpine swamp meadows having the thinnest ALT and alpine desert steppes the thickest. An empirical model developed with readily available meteorological data demonstrated satisfactory accuracy, offering an effective tool for ecological and infrastructure planning in permafrost regions. The findings of this study contribute to the understanding of permafrost degradation due to climate change.