Climate is an important factor that affects the livability of a region. The climate suitability of a region's environment for human settlement profoundly affects the regional socio-economic development and the population distribution. Tibet is an area that is sensitive to climate change. Given the impact of global climate change, the climate suitability of Tibet has undergone significant changes. In this study, the temperature humidity index (THI) values for Tibet were calculated, and the relationships between the population distribution and the THI were analyzed quantitatively. In this way, the zoning standards for climate suitability in Tibet were determined such that the climate suitability could be evaluated. The results show that the average annual temperature in the southeast of Tibet, where the population was densely distributed, was relatively high. The mean annual relative humidity showed a trend of gradually decreasing from south to north. Regions with a suitable climate, including the high suitability areas (HSAs), the moderately suitable areas (MSAs) and the low suitability areas (LSAs), accounted for only 7.90% of the total area but accommodated over 40% of the total population. The critically suitable areas (CSAs) accounted for 37.81% of the land area and 48.24% of the total population. Non-suitable areas (NSAs) were widely distributed in Tibet and accounted for 54.29% of the total area and 11.33% of the total population. The results of this study may provide a reference for guiding the reasonable distribution of population and promoting the optimization of the spatial planning in Tibet.