Grassland degeneration has resulted in a series of social,economic and ecosystem environmental problems,so monitoring changes in grassland is very important. With the development of technology,Remote Sensing(RS)and GIS provide new means for the study of grassland degeneration. Based on the classification of grassland degradation degree calculated by vegetation coverage,we introduced the Grassland Degradation Index (GDI)to characterize grassland degradation in our focal area. The value range of GDI is from 0 to 5. When GDI is large, it means that the area of grassland degradation is more serious. When GDI>4,it means there is extremely severe degradation and when GDI <1,it shows that there is no degradation of pasture in the area. Hulun Buir Grassland was dynamically monitored from 2003 to 2012 using long time series of MODIS data and the two indicators of vegetation coverage and GDI. Finally,the driving force of changes during the ten years were analyzed combined with meteorological data. The results indicate that the Hulun Buir Grassland Ecosystem is fragile,and interannual variability of GDI is dramatic. There is spatial heterogeneity in the grassland degradation degree:grassland degrades more seriously in the west than in the central and eastern regions. In recent years, however,grassland degradation in the central and eastern region has aggravated while the west region has improved. Moreover,the comprehensive analysis of meteorological and artificial factors shows that changes in Hulun Buir Grassland Ecosystem quality are mainly affected by extreme climate,mining and industrial construction.