Our study investigated 12 study sites in four main islands of Tho Chu archipelago in 2019. Six Sargassum species were recorded for the flora of Tho Chu Archipelago, aquifolium (Turner) , Sargassum feldmannii Pham-Hoang Ho, Sargassum ilicifolium (Turner) , Sargassum mcclurei Setchell, Sargassum oligocystum Montagne, Sargassum polycystum , among which three species, namely Sargassum oligocystum Montagne, Sargassum feldmannii Pham-Hoang Ho and Sargassum mcclurei Setchell were newly recorded for Vietnam. There was a significant difference in species composition between Tho Chu, Hon Xanh, Hon Tu and Hon Cao islands; among them, Hon Xanh island differed from the other three islands by 28%, Hon Tu island and Tho Chu island were mostly similarity in flora composition with the similarity index of . The morphology of some Sargassum species varied by ecological characteristics, especially for Sargassum aquifolium (Turner) C. Agardh and Sargassum oligocystum Montagne. | Diversity of the genus Sargassum Fucales Sargassaceae in Tho Chu archipelago Kien Giang province
