The vascular plants in Co Lung commune, Pu Luong Nature Reserve, Thanh Hoa province, were surveyed and identified with 262 species, 201 genera and 98 families of the 4 divisions. The number of useful plant species of the Co Lung, Pu Luong flora was categorized as follows: 95 species for medicinal plants, 31 species for timber plants, 17 species for food and food stuffs, 8 species for ornamental, 21 species for essential oils. The plant species in Co Lung, Pu Luong are mainly comprised of the tropical elements (72.16 percent) of them, the endemic elements with 18.43 percent. In the relationship of species with floras in Asia, the flora in Co Lung, Pu Luong has an affinity with that of Indochi-Indu (6.27 percent), Indochina-Malesia (13.73 percent), Himalaya (9.41 percent), South of China (10.20 percent) and Indochina (7.06 percent). The Spectrum of Biology (SB) of the flora in Co Lung, Pu Luong is summarized, as follows: SB = 80,53 Ph + 6,49 Ch + 2,29 Hm + 3,82 Cr + 6,87 Th.