To understand the effects of human activities and climate changes on sandy grassland vegetation in north China, a field grazing and enclosure experiment was conducted from 1992 to 2006 in Horqin Sand Land, Inner Mongolia. The results showed that: (1) the grazing had significant effects on grassland vegetation, in that the continual overgrazing could result in severe degradation of the vegetation, the light grazing was favorable to restoration of the height, coverage, richness and diversity, and the moderate grazing didn't induce decrease of the richness and diversity thought it also resulted in decrease of the height and coverage; (2) The enclosure could promote increase of the height, coverage, richness and diversity, the increased speed was the height ＞ the coverage ＞the richness ＞the diversity; (3) the warm and wetness climate was favorable to maintain higher the height, coverage, richness and diversity in the sandy grassland, and the warm and dry climate could resulted in significant decrease of the height, coverage, richness and diversity; and the effects of the temperature on the vegetation was greater in the rainy period and the effects of the rainfall on the vegetation was greater in the drought period.