Sonjook island is located Samsan-myeon, Yeosu-si, Jeollanam-do. All of field information was collected from January 2001 to November 2002. The vascular plants recorded as total 584 taxa, 5 forms, 60 varieties, 519 species, 365 geneta, 113 families. Sonjook islands shows the typical vegetations including the lower area of temperate region of Korean peninsula and evergreen broad-leaved forests, Pinus thunbergii forest. The Korean endemic plants were recorded as 13 taxa (5 variety, 8 species, 10 genera, 10 families), 4 taxa as rare and endangered plants (Psilotum nudum (L.) Griseb., Milletia japoniea A. Gray, Arisaema negishii Makino, Sarcanthus scolopendrifolius Makino). The naturalized plants were 23 taxa (20 genera, 9 families, 8.2％ among the total naturalized plants in Korea. This area is ecologically important place that Korea endemic plant, rare and endangered plants ranges much than area. On the one hand, threat from degraded by environmental pollution that share of naturalized plant rises gradually augment. Strong conservation policy and development control should be considered.