Abstract: Freshwater diatom from Hainan island were studied in this research, and 11 of 40 taxa were identified as newly recorded species of China that include Achnanthes islandica Östrup, Achnanthidium archibaldianum (Lange-Bertalot in Lange-Bertalot & Krammer) Lange-Bertalot, Achnanthidium caledonicum (Lange-Bertalot in Lange-Bertalot & Moser) Lange-Bertalot, Achnanthidium deflexum (Reimer) Kingston, Achnanthidium rivulare Potapova & Ponader, Planothidium frequentissimum (Lange-Bertalot) Round & Bukhtiyarova, Planothidium piaficum (Carter & Denny) Wetzel & Ector, Platessa brevicostata (Hustedt) Lange-Bertalot in Krammer & Lange-Bertalot, Platessa hustedtii (Krasske) Lange-Bertalot in Krammer & Lange-Bertalot, Platessa montana var. tropica (Hustedt) Lange-Bertalot in Krammer & Lange-Bertalot, Cocconeis placentula var. acuta Meister. Morphological features and distribution pattern of 11 taxa were described and compared with similar species. The morphological description of the genus Platessa was given in Chinese.