[Objective] An improved remote sensing ecological index model suitable for high vegetation area was constructed to better monitor and evaluate the ecological quality of hilly areas, and the influencing factors of ecological quality were explored, in order to provide scientific support for the balance between development and ecology at Taojiang County, Yiyang City, Hunan Province. [Methods] To address the saturation limitations of the normalized difference vegetation index (NDVI) in densely vegetated areas, the improved remote sensing ecological index (MRSEI) was used to quantify the temporal variation in the ecological environment quality of Taojiang County from 2000 to 2021. Additionally, a geographic detector model with optimized parameters was utilized to analyze the driving forces behind six influencing factors, including vegetation coverage, precipitation, temperature, land use, elevation, and population density. [Results] ① Compared with the RSEI model, the MRSEI model more effectively addressed the issue of NDVI saturation in areas with high vegetation cover, enabling a more precise monitoring of the ecological environment in Taojiang County. ② The average RSEI values for the five periods from 2000 to 2021 in the study area were 0.77, 0.84, 0.83, 0.75, and 0.79, respectively, indicating a satisfactory performance in ecological environmental quality with a trend of improvement-deterioration-improvement. ③ From the analysis of the factors influencing ecological environmental quality, land use emerged as a key determining factor in the study area. In the interactive factor detection analysis, the interaction between land use and elevation was the strongest. [Conclusion] The improved RSEI model could accurately evaluate the eco-environmental quality in high-vegetation areas. The eco-environmental quality of Taojiang County was generally at a good level and showed an upward trend from 2000 to 2021. The change of eco-environmental quality was mainly affected by both natural and human factors.