Abstract: 1. The vegetation of the Xizang plateau is different from the general vegetation of "horizontal zones" and it is also different from that of "vertical zones” in mountainous country. It belongs to the vegetation of vertical zones of the "peneplain pattern”. Therefore, it may be called the vegetation of "plateau zones". 2. The zonation of vegetations in Xizang changes from the southeast to the northwest as follows: forest–meadow–steppe–desert. The formation of these plateau zones is determined mainly by the elevating of the plateau to such a great extent that the particular regime of air circulation was obtained. The wet'southwest monsoon is the fundemental factor for the development of the tropical and subtropical mountain forests in southeast part of Xizang. The plane of the plateau is under the control of the westerly wind circulation and "Qinghai-Xizang" high pressure. Under the in-fluence of such continental climatic conditions on the plateau, the high-cold meadow, steppe and desert vegetations are formed.