As the impacts of global climate change and human activities intensify, monitoring and assessing ecological environmental quality (EEQ) is crucial for sustainable development. This study takes the Northern Slope Economic Belt of the Tianshan Mountains (NSEB of the Tianshan Mountains) as an example, using Landsat satellite imagery data from 1996 to 2023. Based on the Google Earth Engine (GEE) platform, we constructed a Remote Sensing Ecological Index (RSEI) to evaluate the spatiotemporal characteristics of ecological environment evolution in this region. Through Principal Component Analysis (PCA), we integrated four key RSEI: greenness, humidity, dryness, and heat, to reveal the main driving factors of EEQ changes. The research results indicate that: 1) From 1996 to 2023, the overall EEQ in the study area showed a deteriorating trend. However, the EEQ in places such as Tacheng City and Shuanghe City, Xinjiang Uygur Autonomous Region, China, has improved year by year, while the EEQ in Hoboksar Mongol Autonomous County and Alashankou City, Xinjiang Uygur Autonomous Region, China, has deteriorated annually. 2)The degradation of the EEQ in the NSEB of the Tianshan Mountains is greater than the improvement, with degraded areas accounting for 50.93% and improved areas accounting for 3.05%. In the future, the EEQ in most regions is expected to show an improving trend, covering 42.27% of the total area. 3)The analysis of the driving factors of the EEQ using geographic detectors indicates that both human and natural factors significantly impact EEQ, with land use change having the greatest influence.