Global warming during the last century is less doubled internationally. The warming trend in the past 20 years is especially distinctive which makes the phenology and productivity of vegetation change remarkably. Based on NOAA/AVHRR data, combined with the observed meteorological data, a case study on the response of the grassland in the Hulun Buir Steppe of Northeast China to global warming in the past 20 years is made in this paper. It is found that, (1) The temperature in the Hulun Buir Steppe has increased remarkably than that in the global during the last 18 years; (2) The 4 selected areas averaged NDVI in growing season (from April to October) has obviously increased by 2.2% in the past 18 years; (3) The obvious increase of NDVI happened around 1988, when the mean NDVI during 1988~1999 is 7.8% more than that during 1982~1987. (4) Response of the Hulun Buir Steppe to the globe warming is remarkable. The NDVI and the temperature, especially the temperature in spring, have sensitive positive correlativity.