The exploration ,collection and study on taxonomy of vascular plants in Koh Tao Mo, Koh Phra and Koh Phra Noi, Chon Buri Province were made from November 2000 to March 2003, 122 species, 4 subspecies and 5 varieties were explored, collected and classified into 106 genera within 55 families. Among these, Euphorbiaceae has the highest number of species, i.e. 15 species in 12 genera. The second highest number of species were Rubiaceae, i.e. 8 species in 7 genera. Whilst 26 families have 2-4 species in each, and the least number of species, i.e. 1 species were found in 27 families. According to the available taxonomic literatures and specimen, Pterospermum littorale Craib var. littorale, were found as endemic species in this study area. And one rare species is Tarenna hoaensis Pit. Taxonomic description and keys to genera and species were prepared together with taxonomic literature, ecology, geographical distribution, uses, colour photographs of each species. The collected specimen were deposited at the Professor Kasin Suvatabandhu Herbarium, Department of Botany, Faculty of Science, Chulalongkorn University and plant genetic conservation Project under the Royal Initiative of Her Highness Princess Maha Chakri Sirindhorn Herbarium, Chitralada palace, Bangkok.