Abstract: Saur-tarbagatai Mountains,which join with several large floras,lie in the northwest of China.Their geographical location is very special.This article analyses the characteristics of the flora according to arealtypes structure of the species which can be divided into 12 arealtypes and 3 arealsubtypes.The results show that the species with northsouth distribution pattern occupy one third of the total species,this flora has much exchange with south and north floras,it is the important channel of the species moving between south and north floras.It also becomes the distribution boundary of some upland species because of the low altitude of this area.The xeric species distributed in the plains and the front of mountains have not been affected by the topography of this area.

Key words: Saurtarbagatai Mountains