Abstract: The Ruoergai Plateau as an island mountain plateau 3300-4000 meters above sea level is the largest bog land on plateaus in the world. The author carried out spore-pollen analysis of 106 samples from 5 peat profiles on the plateau, determined ¹⁴C dating of 11 samples, and studied evolution law of vegetation in the last ten thousand years and relationship between climatic features and special plateau environment. The spore-pollen groups were dominated by herb pollen, followed by xylophyta pollen, pteridophyte spore content was the lowest. The reflected vegetation type mainly consisted of sedge-dominated subalpine meadows and subalpine bushes. The micro environment of developing peatland was sedge-dominated swampy meadow. But in the Holocene, evergreen conger forest mainly with pine and broadleaf tree forest mainly with Quercus and Birch increased, climate got warm obviously, temperature was 4℃ higher than now. It was the time of most suitble climate. Based on the vegetation succession law, the climate in the Holoeene can be divided into 3 stages-early, middle and late. The climatic change was cold-damp→warm, humid→cold-slight dry, basicly corresponding to the climatic change all over the world. But the climate on the plateau was special because it was controlled more greatly by the hight than the lattitude. The vegetation change was not so obvious as plain area. The range of climate variation was little. Under the long cold damp climatic condition, plant residues decomposed weakly and peat accumulated continually to form large peat deposits.