Timberline, the transitional ecosystem between the uppermost closed montane forests and the treeless alpine meadows, is sensitive to climate change and has long attracted the attention of scientists in many fields of study. Previous research on timberline commonly focused on the relationships between timberline elevation and temperature factors to identify the common controlling factors. Many isotherms thus have been proposed to predict the existence of timberlines in mountain regions. Those isotherms commonly used include the mean temperature of 10℃ for the warmest month (MTWM), mean annual biotemperature (ABT) of 3℃, warmth index (WI) of 15℃·month, etc. However, actual geographical distribution of timberlines often deviates from these isotherms. For examples, MTWM could be as low as 5-6℃ at tropical timberlines and as high as 15.8℃ in Norway. Moreover, a certain type of isotherm cannot reflect or completely cover up the diversity and complexity of timberline environment in different regions. To explore the temperature diversity of timberlines, we compiled data for 410 timberline sites in the Eurasian continent from published literatures; calculated seven thermal variables from published WorldClim dataset that are potentially associated with timberline elevation; and analyzed the variation of these climatic factors. The results reveal that:1) although all temperature variables at timberline positions in the Eurasian continent have wide ranges, MTWM, ABT and WI, which are the representative climate indexes of growing season temperature, have a relatively narrow range. For example, MTWM varies from 6.95℃ to 15.64℃. This indicates that growing season temperatures are key climatic indexes for timberline existence in the Eurasian continent. 2) Temperature indicators associated with timberline elevation vary greatly across different climate zones. In the tropical humid zone, ABT is 4.63℃, WI 21.72℃·month, AMT (annual mean temperature) 3.56℃; in the subtropical humid zone, ABT is 4.32℃, WI 19.19℃·month, MTWM 10.69℃; in the Mediterranean zone, ABT is 5.25℃, WI 29.37℃·month, AMT 4.46℃; in the temperate marine zone, ABT is 3.73℃, WI 16.14℃·month, MTWM 10.31℃; in the temperate continental zone, ABT is 4.01℃, WI 21.47℃·month, MTWM 12.24℃; in the subarctic relatively marine zone, ABT is 2.98℃, WI 12.55℃·month, CI (Coldness index) 80.88℃·month; in the subarctic relatively continental zone, ABT is 2.99℃, WI 15.47℃·month, MTWM 12.06℃; in the temperate zone of the Tibetan Plateau, ABT is 4.04℃, WI 18.02℃·month, MTWM:10.3℃; and in the subfrigid zone of the Tibetan Plateau, ABT is 4.18℃, WI 23.1℃·month, MTWM 12.5℃. 3) Of the commonly used timberline indicators, 10℃ MTWM is only effective in the temperate oceanic, subarctic oceanic, and plateau temperate zone; 3℃ ABT and 15℃·month WI work well only in the subarctic zone. This study reveals the heterogeneity and complexity of timberline habitats in the Eurasian continent. Temperature differences of timberlines may be due to the lack of timberline species like Abies and Picea in the Mediterranean zone, drought and precipitation deficiency, mass elevation effect, etc.