Under the trend of frozen ground degradation caused by global warming， the study on the spatial-temporal evolution and driving forces of ecological environment quality in different frozen ground regions of the Three-River Headwater Region （TRHR） can provide a theoretical basis for regional ecological environment governance and ecological civilization construction. The remote sensing ecological index （RSEI） was constructed based on the MODIS data set of google earth engine from 2000 to 2022， and the spatial-temporal evolution of ecological environment quality in different frozen ground regions of the TRHR was explored by coefficient of variation， migration of gravity center， Theil-Sen slope estimation， Mann-Kendall test， and Hurst index. The driving force of natural and human factors on the spatial differentiation of ecological environment quality was compared and analyzed by Geodetector. The results showed that： ① From 2000 to 2022， the ecological environment quality of the TRHR was at a medium level as a whole， showing a spatial distribution pattern of "low in the northwest and high in the southeast" . Among them， the mean value of RSEI in different frozen ground regions were： predominantly continuous and island permafrost region （0.630） > mountain permafrost region （0.624） > middle-thick seasonally frozen ground region （0.587） > predominantly continuous permafrost region （0.429）. ② In the past 23 years， the ecological environment quality of the TRHR was improved as a whole， the rising rate of RSEI was 0.001 5 a-1， and the center of gravity of each grade of RSEI migrated to the interior of predominantly continuous permafrost region. More than 57.00% of the frozen ground regions showed an improvement trend， and the middle-thick seasonally frozen ground region reached 73.37%. ③ In the future， the ecological environment quality of the TRHR will be generally anti-sustained in the future， and the frozen ground regions will be dominated by a slight deterioration trend. The area of deterioration trend in the middle-thick seasonally frozen ground region will be the largest （61.95%）. ④ Precipitation was the dominant factor for the spatial differentiation of ecological environment quality in different frozen ground regions of the TRHR， and the influence of human factors was not significant. The driving force of the multi-factor synergy was greater than that of the single factor， and the interaction between precipitation and temperature factors had the strongest explanatory power. The driving factors of each frozen ground region were different， so ecological management policies should be tailored to local conditions in different frozen ground regions.
Keywords: Three-River Headwater Region; ecological environment quality; frozen ground region; geodetector; remote sensing ecological index（RSEI）; spatial-temporal evolution.