Abstract: The largest area and most pristine tropical rainforests in South China are preserved on Yinggeling Mountain, Hainan Island. In order to identify the floristic elements and the importance of the spermatophyte flora, we carried out extensive fieldwork during 2003–2006. A total of 1,706 species were recorded, belonging to 825 genera and 173 families. At the generic level, tropical elements were the dominant components, in which pantropical genera and tropical Asian genera contributed 25.28% and 32.36% of the total (excluding cosmopolitan genera), respectively. There were eight genera endemic to China, including two genera (Pyrenocarpa and Metapetrocosmea) endemic to Hainan Province. At the species level, tropical elements contributed 70.50% of the total number of species (excluding the cosmopolitan ones). There were 474 species endemic to China, accounting for 28.42% of the noncosmopolitan species. Among them, 149 species (31.44%) were endemic to Hainan. Yinggeling Mountain has a unique flora, exhibited not only by newly re-corded and unusual species, but also by being a geographical nexus of subtropical flora with typical tropical species, xerothermic with humid and warm species. Compared with the flora of four neighboring areas, the flora of Yinggeling Mountain showed high similarity with that of Diaoluo Mountain, but contained more tropical elements than Dinghu Mountain of Guangdong and Xishuangbanna of Yunnan.