Abstract: Since the Dongting Lake basin is a significant ecological zone in the middle and lower reaches of the Yangtze River, quantitative monitoring and evaluation of its ecological environment serve as a prerequisite for regional ecological conservation, restoration, and governance. Using MODIS products involving 2010—2019 remote sensing data, this study constructed the remote sensing ecological index (RSEI) for the Dongting Lake basin based on four ecological indices: greenness, humidity, dryness, and heat. Furthermore, this study explored the spatio-temporal dynamic characteristics of the ecological environment in the basin and their influencing factors. The results show that: ① From 2010 to 2019, the Dongting Lake basin exhibited an elevated greenness index, a reduced humidity index, and relatively stable dryness and heat indices; ② The ecological environment of the Dongting Lake basin was generally satisfactory, with a mean annual RSEI of 0.58, indicating a fluctuating growth. In terms of spatial distribution, the ecological environment in the western and surrounding areas was superior to that in the eastern and central areas; ③ There were strong correlations between RSEI and precipitation, air temperature, elevation, and land cover. The RSEI was the highest (0.65) for forest land and the lowest (0.31) for construction land. As for the two primary land conversion types (grassland → forest land, arable land → grassland) in the basin, the former type could improve the regional ecological environment (ΔRSEI=0.002 5, a contribution rate of 46.3%), whereas the latter type might lead to ecological environment deterioration (ΔRSEI=-0.000 4, contribution rate: 44.44%). The results of this study, assisting in deeply understanding the spatio-temporal characteristics of the ecological environment in the basin and their internal driving mechanisms and facilitating scientific land planning and ecological environment governance, hold critical theoretical and practical significance.