Vegetation and climate changes since Miocene were studied preliminarily in terms of palynological and paleobotanical records in the Qinghai -Xizang plateau in Miocene,subtropical alpine sclerophyllous oak forest existed in the most parts of Xizang,espicially southern Xizang. Meanwhile,the altitudinal zones of vegetation appeared and the alpine shrubbery was found firstly.The climatic characteristic was middle moist with annual temperature at above 2～ 10℃. In Early and Middle Pliocene,due to that rising mountains gradually hindered the India Ocean Monsoon’s entering,the subtropical alpine sclerophyllous oak forest distributing widely in Miocene moved southward,main vegetation was evergreen sclerophyllous oak-cedra forest found in the regions south to the Gangdisi and Nianqingtanggula Mt., where the annual temperature was above 10℃ higher than today estimated by its modern distributing altitude, montane evengreen coniferous forest existed in the most of regions north to Gangdisi and Nianqingtanggula Mt, where the annual temperature was about 7℃.Since Late Pliocene,evergreenoak and cedra decreased, deciduous and herberous elements increased, main vegetation was subtropical mixed coniferous,and broadleaved forest in the north slopes of the Himalaya Mt, and regions south to Nianqingtanggula Mt., where the temperature Was 5.2～8.1℃ higher than present,in the regions north to the Himalaya ’s north slopes and Nianqingtanggula Mt. ,drought became worse gradually, which resulted in appearence of shrubbery and steppe,where annual temperature was about 4 ℃ higher than today. Drought was serious since Late Pleistocene in the interior of the Plateau,alpine shrubberysteppe was found in the most part of Xizang, subtropical mixed coniferous and broadleaved forest,subtropical evergeen season rainforest and rainforest only existed in the Zhangmu,Kada,Yadong,Jilong, Cayu and Mutuo in the south slopes of the Himalaya Mt.,Holocene vegetation was similar to the Present.