The purpose of this study was to investigate the structure of the vegetation on the trail of Hallyeo Marine & Coastal National Park. Twenty-six 10×10m plots were established along the Jisim island trail. The vascular plants were surveyed from March 2011 to October 2011. The flora was classifield to 246 taxa; 82 families, 191 genus, 220 species, 2 subspecies, 22 varieties, and 2 forma. Camellia japonica was a major woody species in the study area, while Pinus thunbergii and Zanthoxylum ailanthoides were co-dominant tree species. There were positive correlations between Distylium racemosum and Ligustrum japonicum var. japonicum; Callicarpa japonica var. luxurians and Eurya japonical; Actinodaphne lancifolia and Cinnamomum japonicum; A. lancifolia and Machilus japonica. Positive correlations were found between A. lancifolia and P. thunbergii; Z. ailanthoides and C. japonicum. Species diversity (H′) was ranged from 0.51907 to 1.0217, and was relatively low compared to those of other national parks.