Abstract：Based on 315 images of SPOT VEGETATION data for 9 years during 1998-2006, the dynamic spatial and temporal variation of the vegetation cover in the Zhangye Basin is studied by means of trend analysis and differential analysis. The results show that the vegetation is the best in June and July during 1998-2002 and this period is shifted to July and August during 2002-2006. This shift is caused by a redistribution of water resources in the Heihe River, and an adjustment of industrial structure in Zhangye city, which is followed by a decrease of the area of summer crops, and an increase of the area of autumn crops. The yearly maximum NDVI is on the whole improved, but the trend of change of monthly maximum NDVI sees a great difference among different months. The change during the adjacent two years of both the yearly maximum NDVI and the monthly maximum NDVI witnesses a great difference, and the vegetation degradation and improvement appear fluctuantly. The major changes occur in well-developed region with the artificial vegetation, while the minor changes are in the no-vegetative or partially vegetative desert or the Gobi.