Abstract:[Objective] The driving factors of ecological environmental changes in the Bailong River basin from 1990 to 2020 were determined in order to provide a scientific basis and decision support for the sustainable development of the Bailong River basin.[Methods] Landsat TM/OLI image data from the vegetation growing season (June to September) were obtained from the Google Earth Engine (GEE) platform and screened year by year. From these data, the four ecological indicators of greenness (NDVI), humidity (WET), heat (LST), and dryness (NDSI) were calculated. Principal component analysis (PCA) was used to construct the remote sensing ecological index (RSEI), and the ecological environment of the Bailong River basin was evaluated.[Results] From 1990 to 2020, the mean RSEI value in the Bailong River basin increased from 0.531 to 0.675, indicating that the ecological and environmental quality had generally improved. The area of ecological and environmental quality improvement was mainly located along the two banks of the Bailong River in the Zhouqu-Wudu section, Northwest Tanchang County, and the east bank of the Minjiang River, with an area of 8 393.97 km2, comprising 45.55% of the total area. The influence degree of each ecological index on the ecological environmental quality followed the order of NDSI>WET>LST>NDVI in 1990; NDSI>NDVI>WET>LST in 2006; NDVI>WET>NDSI>LST in 2020.[Conclusion] Using the GEE platform to implement the RSEI model expanded the ability to monitor and evaluate the regional ecological environmental quality over a large area and for a long time period. In recent years, the ecological environmental quality of the Bailong River basin has generally improved, but protection and management of the basin will need to continue.