Based on Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP) downscaling data of simulations generated by five climate (Earth) system models in CMIP5, in this study, the multi-model collection was used to estimate the vegetation growing season and active accumulated temperature changes in the circum-Arctic region in the 21st century under various climate change scenarios. The research results show that: 1) Multi-model ensemble simulation can basically reproduce the observed spatial distribution characteristics of the initial and final frost days, length of the frost-free period, accumulated temperature of >10℃, and change trends of these indicators from 1979 to 2004. However, its ability to simulate the spatial differences and interannual variability of climate change is weak. 2) By the end of the 21st century, the final frost day will advance by up to 60 days, initial frost day will be delayed by 20-40 days, frost-free period will extend up to 100 days, and accumulated temperature will vary by 1000-1200℃. Each of these indicators undergoes the greatest change under the RCP8.5 scenario, and the least change under the RCP2.6 scenario. 3) The changes in the indicators have large spatial differences, with the changes in the central and western parts of the Eurasian continent being generally larger. With the warming of the climate, increases in the accumulated temperature>10℃ gradually show obvious zonality in the latitudinal direction, with a greater increase in the south.