###### Abstract  
The evaluation of ecological environment quality (EEQ) is an important method to measure the quality of ecosystem services. Therefore, the EEQ of Changing County, located in the red soil region of southern China, was assessed by using the remote sensing ecological index (RSEI) based on Landsat images from 1995 to 2019, and its spatiotemporal variability was identified by using the Global Moran's I index, standard deviational ellipse, and kernel density estimation. The results showed that, firstly, the EEQ degraded from 1995 to 2000, then improved from 2000 to 2019; secondly, the spatial distribution of the RSEI for each study year was not random and had a strong positive correlation; thirdly, the directional distributions of the RSEI for all the grades were almost in the direction of southwest to northeast, and the spatial discrete characteristics of the moderate- and good-grade areas were almost consistent from 1995 to 2019; fourthly, the kernel density distribution of the moderate- and good-grade EEQ was located in towns within the Tingjiang River Basin and in the surroundings of the study area, respectively. This study can help managers to better understand the spatial-temporal variations in the EEQ in the study area, supporting the government in formulating a better ecological restoration strategy. ecological environment quality; remote sensing ecological index; spatial-temporal variation; red soil; southern China 202414864114864  
of the EEQ. Non-administrative units have also been examined; for example, because of the special status of nature reserves and basins in the ecosystem, the EEQs of Changbai Mountain Nature Reserve and Ebinur Lake Wetland National Nature Reserve in Xinjiang in China were evaluated based on the RSEI, respectively. The former reserve showed an improvement trend in the EEQ during the study period, where the greenness and wetness indicators had a positive effect on the EEQ, while the dryness and heat indicators exhibited the contrary. In the latter reserve, the overall quality of the eco-environment was ameliorated from 2007 to 2016, and the wetness index had the greatest effect on the EEQ. Compared with those in 2007 and 2016, there was a strong positive correlation within the spatial distribution of the RSEI in 2013 [15; 16]. Similarly, considering the important role of the Yellow River and the Yangtze River in the economic development of China, RSEI evaluation models of the Yellow River Basin and the Jialing River (as an important branch of the Yangtze River) Basin were established and showed an improved trend during the study periods [17; 18]. In addition, RSEI models can be applied in regions with a smaller spatial scale, such as in mining areas [19]. Based on established RSEI evaluation models, the driving force factors and the spatial aggregation characteristics of EEQ have also been further analyzed by scholars; these can not only directly display the spatial-temporal variations in the High-High and Low-Low clustering regions of the RSEI value but can also help us to grasp the cardinal driving force factors affecting the variability in the EEQ by using Geodetector, Moran's I index, etc. [20; 21]. Changing County is a typical representative of the red soil erosion zone of southern China and is one of the counties with the most serious soil erosion [22]. Since 1995, the rapid development of urbanization and industrialization has had a serious effect on the eco-environment. Although, after many years of soil erosion control, the eco-environment of the region had improved, the spatial-temporal variability in the EEQ in the region was still unknown for the period 1995 to 2019. Therefore, we assumed that the selected greenness, wetness, dryness, and heat indices could express most of the characteristics of the eco-environment.