The flora of Qinghai-Tibet Plateau started in late Cretaceous or early Tertiary. Paleobotanical data had showed that there were same or similar flora in Qinghai-Tibet Plateau to Tethyan Tertiary evergreen flora in that time. Along with the gradual climate change of the Tethys, which  had become aridity since Neogene, the evergreen flora was gradually replaced by semiarid or arid flora of the Tethys and only preserved and developed in E Asian and Indo-Malaya. Analysis of some representative groups:Piptanthus, Ammopiptanthus, Anagyris, Arenaria, Kelloggia, Coriaria, Hippophae, Velloziaceae, Meconopsis, Helleborus and sclerophyllus oaks in Qinghai-Tibet Plateau, showed that the uplift of the Qinghai-Tibet Plateau caused the semiarid or arid flora of Tethys evolved to adapt to different environment and differentiated into different elements,i.e. C Asian, Mediterranean-W Asian and C Asian, the temperate of Old World, North Temperate and Sino-Himalayas and others, as well as some disjunction, endemic and relic distribution. Furthermore, the analysis also demonstrated the dispersal pathway of Tethys flora along Tethys to and from east and west, and to from north and south, to Tropical Asia, Africa and South America in early tertiary, which was one of the main reasons causing modern disjunction between Qinghai-Tibet Plateau and Old World Temperate, as well as W America, Africa, S America and tropical Asia.