Abstract: Climate change and human activities continue to intensify and cause some ecological and environment quality problems. It is important to the sustainable and coordinated development of human and nature to quickly and accurately evaluate the historical and current situation of regional ecological environment. In this paper, four indicators including greenness, wetness, dryness and heat were retrieved using the RS means. Principal component analysis (PCA) was used to construct the modified remote sensing ecological index (MRSEI), and the representativeness of MRSEI was analyzed by correlation analysis. Based on MRSEI, the ecological environment evaluation model was developed for the Xilin Gol Steppe, and the overall evaluation of the ecological environment in the Xilin Gol Steppe in recent 26 years was conducted. The results showed that MRSEI could be used to collect the information of various ecological factors and evaluate the ecological environment accurately. From 1991 to 2017, the ecological environment quality in the Xilin Gol Steppe was improved at first and then degenerated. In 1991, the environmental quality in the upstream was better than that in the downstream, and it was better in the eastern part than that in the western part. In 2004, the spatial difference of the overall ecological environmental quality in the study area was obviously changed compared with that in 1991. The ecological environment quality in the upstream was improved but obviously decreased in the downstream. By 2017, the ecological environment quality in the whole study area was roundly reduced, and a good ecological environment was remained only along the upper banks of the Xilin River and the southern and the southeast parts of the drainage basin.

Key words: modified remote sensing ecological index, principal component analysis, ecological factor, environment evaluation, Xilin Gol