Abstract:The area to the north of Qilian Mountain is one of the most important areas in northwest China. Recently, the eco-environment in this area has drastically degradated and Ejina Banner has been turned from an ecological barrier into one of the sources of sandstorm. On the basis of quantitative remote sensing results, this paper studies the variation trend of NDVI from 1982 to 2002 in the area to the north of Qilian Mountain by using GIMMS NDVI data. It is shown that the variation trend of secular NDVI is rising in Jiuquan, Zhangye, Wuwei and Jinchang basins. On the other hand, the variation trend of secular NDVI in Ejina Banner, which is located in the downstream of Heihe River, is declining and the oasis is shrinking. The mechanism of oasis degradation is also analyzed in this paper.