Vegetation cover is one of the primary indicators of changes to ecosystems. Large scale vegetation cover observations will indicate the effect of natural factors and human activities on the ecological environment,so it is one of the hot topics in global change research. The Yellow River Basin is located in an arid,semi-arid and semi-humid area and its ecological environment is vulnerable. In recent years,the vegetation in the Yellow River Basin has had a relatively large variance in spatial and temporal patterns,affected by changes in climatic conditions and perturbations from human activities. Therefore,improving the observation of vegetation will provide us with more information about vegetation status and make us better able to understand the variations of ecological environment characteristics. With this background,this paper provides an analysis of spatio-temporal variations of MODIS / NDVI in the vegetation covered area of the Yellow River Basin. The MODIS product,which is assumed to be suitable for large scale observations of vegetation variation,was used,and MOD13Q1 data with a spatial resolution of 250 m × 250 m from 2000 to 2010 was utilized as the data source. NDVI was used as a proxy for vegetation cover and the Theil-Sen Median trend analysis with the Mann-Kendall test were both used to analyze NDVI trends as they are new methods in the long term series analysis of NDVI. Theil-Sen Median trend analysis was used to describe the trend of NDVI and the Mann-Kendall test was used to estimate the significance of trend. The combination of the result of Theil-Sen Median trend analysis and Mann-Kendall test,as well as the result of Hurst index were conducted to analyze the sustainability in NDVI trend. The results indicate that: 1) From the distribution of the annual NDVI in the Yellow River Basin,the NDVI values are high in the west and the southeast,but low in the north; 2) From the time variation of annual NDVI in the vegetation covered area in the Yellow River Basin,the values of NDVI fluctuate between 0. 3 and 0. 4,from 2000 to 2010,and NDVI from 2000—2004 shows high fluctuations,but rapid upward trend since 2005; 3) From the spatial trends of NDVI,the area where the values of NDVI increase is much larger than the area where the values of NDVI decrease and the area where the values of NDVI increase occupies 62. 9% of the vegetation covered area,while the area where the values of NDVI decrease accounts for 27. 7%. 9. 4% of the vegetation covered area remained unchanged,during the period of 2000— 2010; 4) From the spatial sustainability of NDVI trend,the overlaid result of the Theil-Sen Median trend analysis,MannKendall test and Hurst index indicates that 86. 0% of the area presents a positive sustainable development. From the overlaid result of the Theil-Sen Median trend analysis and Mann-Kendall map and Hurst index map,it can be concluded that 53. 7% of the vegetation-covered area presents a sustainable-increased state,7. 8% of the vegetation-covered area presents a sustainable-unchanged state,24. 5% of the vegetation-covered area shows a sustainable-decreased state and 14. 0% of vegetation-covered area cannot be identified in the future. These areas need to be focused upon and further researched.