Abstract: The Dipterocarp forest occuring in the south of Mengia County, Xishuangbanna, is a forest type of tropical rain forest from the northern margin of tropical zone of SE Asia. This for-est, covering about 800 hm2, is estimated to consist of 642 species of vascular plant belonging to 355 genera and 122 families, of which seed plants share 622 species of 340 genera of 109 families and ferns shares the others. In this forest, Rubiaceae with 54 species is the largest family in size and other families are arranged in sequance as following: Lauraceae(35 species), Euphorbiaceae(28), Annonaceae (28), Moraceae (25), Orchidaceae (23), Meliaceae (22), Vitaceae (15), Apocynaceae (13) and Fagaceae (12) etc.. Dipterocarpaceae, Guttiferae, Icacinaceae and Myristicaeae etc., though containing a few species separately, show higher importance value in-dex in this forest community.

Key words: Xishuangban