Abstract: Located in the north-edge of tropical Asia,the flora of Hainan Island has ancient tropical floristic compositions as well as ancient subtropical floristic compositions of China,due to its diversity of natural landforms and climate.In this paper,we chose coastal and hilly areas such as Liudaoling Nature Reserve,Huoling Nature Reserve,Luhuitouling Mountain,Nanshanling Mountain and Hongxialing Mountain(which all locate in the southern Island and are called QN below),and Tongguling Nature Reserve(which locates in the northern Island and is called QB below) as research areas.After surveying the plots,we obtained enough data and compared floristic compositions of two areas.Results show that floristic compositions of both areas had similarities and differences:In QN,there are 876 species of spermatophyte,belonging to 112 families and 484 genera.Geographic elements include tropical ones,temperate ones and Chinese endemic ones.Tropical elements are dominant and Hainan endemic ones are rich,which shows it is transitional elements;In QB,there are 934 species of spermatophyte,which belong to 141 families,580 genera.Geographic elements,which include tropical ones,temperate ones and endemic ones,are dominated by tropical elements and rich in Hainan endemic elements.The common characteristics of flora components of two areas are that plant species are abundant,geographic elements are diversified,dominant elements are significant and proportion of tropical elements is high.