Abstract: The ecoenvironment is highly related to human life. Remote sensing technique can objectively and quantitatively evaluate the spatial and temporal variations of ecoenvironment quality and thus provide a scientific basis for regional eco-environment management. Based on the Google Earth Engine (GEE) platform, we adopted Landsat TM/OLI remote sensing images as the basic data source to calculate the remote sensing ecological index (RSEI) that reflects the ecoenvironment quality. Using RSEI, we evaluated the eco-environmental quality of Qilian Mountain National Park during 1989-2019 and analyzed the reasons. The results showed that RSEI performed well in assessing the eco-environment quality of Qilian Mountain National Park. Greenness and wetness were the two indices with positive effects on the eco-environment quality, while dryness and heat indices had adverse effects. The analysis of spatial and temporal variations in Qilian Mountain National Park showed that the eco-environment quality presented a trend of “slow decline  rapid decline  increase” during 1989-2019. Changes in eco-environment quality were stable from 1989 to 1999, mainly mildly deteriorated from 1999 to 2009, and mainly mildly improved from 2009 to 2019. The analysis of the causes of eco-environment quality showed that the effects of all the four indices were significant. The strength of natural factors in influencing ecoenvironment quality were in order of greenness > dryness > wetness > heat in 1989; heat > greenness > wetness > dryness in 1999; dryness > heat > wetness > greenness in 2009; and greenness > wetness > dryness > heat in 2019. Animal husbandry was an important factor affecting the eco-environment quality of Qilian Mountains National Park. Our results suggested that the GEEbased platform could be used as a computing platform to evaluate the eco-environment quality of Qilian Mountain National Park. This platform extends the application of RSEI in the evaluation of eco-environment quality at large scale and long time series. The eco-environmental quality of Qilian Mountain National Park has developed in the right direction in recent years, although comprehensive management work needs further improvement.

Key words: eco-environment, Google Earth Engine, remote sensing ecological index (RSEI), principal component analysis, Qilian Mountain National Park.