This paper extracts grasslands greenup from SPOT-VGT NDVI filtered by D-L during 1999 to 2012, and uses ground greenup date to verify the result. The main conclusions are as follows: (1) A new method, which combine grassland vegetation remote sensing regreening stage monitoring and ground validation, is presented. Greenup date of Xilingol grassland is extracted by using dynamic threshold coefficients of 25% and its precision can reach 68%. (2) The mean greenup date in Xilingol league is mainly observed from early April to late May. The greenup dates are delayed from south to north, with the average change being-1.5 d/lOa. Exploring spatiotemporal characteristics of grasslands phenology in Xilingol i of theoretical and practical significance in China's combat to climate change, grassland protection and management in the presence of specific problems, decision making in local agricultural and animal husbandry, and vulnerable grassland ecosystems rehabilitation.