The Yangtze River Economic Belt (YREB) is a key eco-environmental protection barrier and economic engine in China. Understanding the characteristics of its eco-environmental spatiotemporal evolution and mechanisms driving these changes is important for revealing shifts in ecosystem structure and function. However, the governing elements of the ecological environment and how these components interact remain unclear due to the strong coupling impact of urbanization and climate change. This paper constructed a long-term series remote sensing based ecological index (RSEI) to evaluate the characteristics of eco-environmental variation of YREB since 2000. Subsequently, the fundamental reasons of the eco-environmental evolution were quantitatively analyzed using optimal parameters-based geographical detector (OPGD). Results indicated: 1) The average RSEI of YREB was 0.68, indicating a rather high overall eco-environmental quality (EEQ), with 73% of the region having RSEI values more than 0.60. The regions with excellent conditions were concentrated in Zhejiang, Jiangxi, Guizhou, and Hunan, while the poorer areas were in northwestern Yunnan, southwestern Sichuan, and western Hubei. 2) The EEQ of YREB mainly showed a degradation trend, with degraded areas exceeding 80% over the past 25 years. In the future, most areas might face higher risks of ecological degradation. 3) DEM, temperature (Tem), and population (POP) were key driving factors of the ecological environment. There were significant interactions between certain factors, with the interaction between DEM and potential evapotranspiration (Pet) explaining 62.2% of the ecological quality distribution. The findings assisted the creation of an ecological civilization by offering policy proposals for managing and conserving ecological environments.