The characteristics of temporal and spatial variations in the grass growing season of Tibet during the period of 1982 to 2010 were analyzed using NDVI data and GIS technology. Results show that the grass growing season of Tibet is short and only four months per year. During the research period, the ND-VI of grass growing season shows increasing trend, but the increase of NDVI is slow and the rising rate is only 0. 009 ? (10 a)~(-1). The cumulative growth rate is 15. 24%. The NDVI of grass growing season decreases from southeast to northwest in Tibet and the high value of NDVI is located in the Naqu and Changdu of northeast Tibet. The NDVI of grass growing season elevates from 1982 to 2010 accounting for the 71. 77% of total grassland area. The NDVI of grass growing season in the south wing of eastern Himalaya area in southern Tibet is significant increase,while the NDVI in parts of the Yarlung Zangbo River is significant decrease during the period of 1982 to 2010. The above results indicate that human beings do not have a devastating effect on the grassland vegetation coverage of the area in recent 30 years. The change of climatic condition in the central areas of Tibet is unsuitable for vegetation growth. Vegetation in the north central and northwest region of Tibet is the most sensitive part in response to climate change.