Sixteen meiofauna groups were found at the study sites and Foraminifera was the most dominant group. Composition and density of meiofauna at the study sites were significantly different. Foraminifera, Turbellaria, Nematoda and Polychaeta were the meiofauna groups which were significantly different among island groups. Foraminifera was found relatively high at Mu Ko Samed and relatively low at Mu Ko Angthong. Copepoda, Ostracoda and Gastropoda were found relatively high at Mu Ko Angthong. Gastropoda was also found relatively high at Ko Kut-Ko Mak. The total densities of meiofauna showed negative correlation with the grain sizes. However, the data analysis for each meiofauna group revealed that the densities of Foraminifera and Copepoda showed no correlation with grain sizes.