AbstractTo explore the altitudinal differentiation of flora of Mt. Gongga and its relationship with those of surrounding areas, we investigated eight vertical vegetation zones on the eastern slope of Mt. Gongga, and analyzed the altitudinal distribution, the floristic components at the level of family, genus and species, and the contrast between different vegetation zones. Major results are as follows： (1) temperate flora primarily dominates the vegetation along the altitudinal gradient, but tropical and temperate components are equally abundant at the arid valley bottom area. The composition and altitudinal distribution of the tropical elements indicate the remnant effects of the Paleotropical and PaleoMediterranean flora; (2) East Asia and East Asia-North America arealtypes have the greatest influence on the forest flora in the middle part of Mt. Gongga, which are chiefly ancient temperate components; (3) North Temperate arealtype is the main body of the flora of Mt. Gongga, and comprises the bulk of the advanced and endemic components in the flora since the rise of the Tibet Plateau. It represents the young components of the flora, and (4) a wide range of Chinese endemic species comprise about 40%－65% of the flora of different vertical vegetation zones, increasing in dominance at higher elevations. At middle elevations, the flora of Mt. Gongga most closely relate to the flora of central China; at the alpine zone, the connection between Mt. Gongga and Tibet Plateau and East Himalayan Mountains takes precedence. The biogeographical significance of Gongga Mountain and the properties of the flora endemism at Mt. Gongga and Hengduan Mountain Range are discussed.