Abstract: The Yangtze River Basin has an important strategic position in China's ecological security pattern and socioeconomic development. However, there exists a lack of long-term monitoring studies on the ecological environment quality in the Yangtze River Basin. In order to explore the spatial and temporal changes of the ecological quality of the Yangtze River Basin, this study utilized Google Earth Engine (GEE) and selected Landsat remote sensing images of the growing season (May-September) from 1990 to 2020. The Remote Sensing Ecological Index (RSEI) was calculated, and the GeoDetector was used for factor analysis. The results indicated: (1) The average contribution rate of humidity, greenness, dryness, and heat on the first principal component was 85.49%, and the average correlation of RSEI was higher than other single indicators. This validated the feasibility of constructing RESI based on the first principal component in the Yangtze River Basin. (2) From 1990 to 2020, the overall ecological environment quality remained at a good level, showing a slow upward trend of decreasing and then increasing. The ecological quality in the middle and lower reaches generally was higher than that in the upper reaches, and the ecological quality in the southern part was higher than that in the northern part. From 1990 to 2005, areas of mild deterioration were relatively scattered. While from 2005 to 2020, areas of mild improvement were mainly concentrated in the Jinsha River Basin, Dongting Lake Basin, and Poyang Lake Basin, and the areas of minor changes were mainly distributed in the central region. (3) The main driving factors were altitude, average temperature and annual precipitation. The results of multi-factor detection showed a synergistic enhancement effect among these factors. (4) Among different land use types, the RSEI value of forest land was the highest, while that of bare land was the lowest. At the county scale, the proportion of forest land had the highest correlation with RSEI and had a positive effect on RSEI, with an average correlation of 0.69; The proportion of impervious surface, population density, and economic density had negative effects on RSEI, with average correlations of -0.39, -0.43, and -0.45, respectively. These findings provided important theoretical and technical support for the ecological environment protection and development of the Yangtze River Basin.