Using the quadrat method, the species diversity characteristic was comparatively studied between native species and exotic species in the 6 residential green areas in Sanya city. The results showed that there were 48 plant species belonging to 22 families and 40 genus in investigated areas, including 17 native species which were belonged to 11 families and 16 genus and 31 exotic trees species which were belonged to 16 families and 28 genus. The dominant species of native species were Cocos nucifera, Ficus benjamina, Sterculia lanceolata, Winchia calophylla and Caryota ochlandra, and dominant exotic species were Spathodea campanulata, Pterocarpus indicus, Ficus religiosa, Terminalia mantaly, Delonix regia, Senna surattensis and Plumeria rubra. Richness indexs of native species were 1.2 - 1.6 and those of ex- otic species were 1.7 -5.8, Simpson indexs （D） of native species were 0. 552 6 -0. 791 5 and those of exotic species were 0. 722 1 -0. 918 4; and Shannon-Wiener indexs （H＇） of native species were 1. 256 6 - 1. 748 6 and those of exotic species were 1. 629 0 - 2. 735 3. The change trend of Shannon-Wiener index, Simpson index, richness index from large to small order was ： all of species 〉 exotic species 〉 native species. It showed that exotic species were introduced sufficiently, and the proportion of native species was less, which should be increased in the future.