Maintaining plant diversity on tropical islands is a priority for biodiversity conservation. Hainan Island, located in the northern tropics, is the second largest island in China with high plant diversity. Several updated plant lists of local flora have been published after decades of field investigations. In this paper, we investigated the plant diversity on Hainan Island by conducting extensive field surveys and a literature re- view. Results indicated that, as of December 2015, there were 6,036 vascular plants recorded on Hainan Is- land with voucher specimens or practical materials. Among these species, 1,220 species were revised as syn- onymously, 4,579 species were wild (including 483 endemic and 512 rare and endangered species), 163 were naturalized species (including 57 invasive species) and 1,294 species were cultivated species. Since the pub- lication of Flora Hainanica in 1964-1977, a large proportion of newly recorded species were mainly wild or introduced species, and accounted for 35.9% and 75.9% of their corresponding totals, respectively.