The vascular plants in Jeju composed of 21 families 62 genera, 190 species, 7 varieties with 197 taxa in Pteridophyta, 3 families 5 genera, 7 species, 3 forma with 10 taxa in gymnosperm (Coniferophyta) and 143 families 703 genera, 1,622 species, 114 varieties and 47 forma with 1,783 taxa in Endospermae. The total number of taxa was 1,990 consisting 167 families, 770 genera, 1,818 species, 121 varieties and 50 forma. Three families, 4 genera 4 species and 1 variety in Pteridophyta and 1 family, 1 genus I species, 1 forma of Coniferophyta were endemic to Jeju. Five families, 8 genera and 8 species in the Monocotyledonae of Endospermae and 23 families, 32 genera, 21 species, 16 varieties and 7 forma and 44 taxa in Cholipetalae, and 9 families, 24 genera, 12 species, 13 varieties and 7 forma, total 32 taxa in Sympetalae were endemic to Jeju. Total 90 taxa with 41 families, 69 genera, 46 species, 29 varieties and 15 forma were drawn up as endemic plants in Jeju. As the numbers show on, Jeju has more biodiversity especially plant diversity than any other places in Korea. It was an important region in regard to geographical position. The rarity on plants from Jeju has been assessed based on the IUCN red list categories and criteria at both regional and global levels. There was one species in each extinct (EX) and extinct in the Wild (EW). The EX and EW species were Rhododendron saisiuense Nakai (Ericaceae) and Asplenium antiquum Makino (Aspleniaceae), respectively. Three taxa, Rhododendron dauricum L. (Ericaceae), Lycopodium sieboldii Miq., and Lycopodiella cernua (L.) Serm (Lycopodiaceae) were species that is extinct in the region (RE). Sixty-one taxa were critically endangered (CR), 13 were endangered (EN), and 83 were vulnerable (VU) at regional level. The taxa listed on a Red List corresponds 26.9% of total taxa in Jeju. At global level, there were 19 taxa in CR, 4 in EN, and 1 in VU (Vulnerable) as the category of threat. The rest taxa (133 taxa) were classified as Least Concern (LC). According to the results of the assessment, conservation measures must be taken for total of 157 species that were categorized in threaten including one of EX, one of EW and three extinct in the region immediately. Of 157 species, 61 were CR, 13 are EN and 83 were VU.