In the paper, 51 genera 92 species of benthic macroalgae are recorded based on the investigation of Dongtou archipelago, including 4 genera 4 species of Cyanophyta, 30 genera 50 species of Rhodophyta, 10 genera 17 species of Phaeophyta and 7 genera 21 species of Chlorophyta. Floristic characteristics of main constructive species of macroalgae: the warm temperate and subtropical species are dominant species which accounted for 64.13% and 26.09% of total species respectively. The characteristics of algae flora show that Dongtou archipelago is a typical transitional area of warm temperate to subtropical. For the substrate and turbidity, the differences between the horizontal and vertical distribution of the macroalgae are great. Furthermore, Comparing macroalgae attached on Sargassum fusiform culture rafts and normal condition, it shows that: light plays an important part in macroalgae growth and multiplication. More attention should be paid to light factor in the future floristic investigation of macroalgae.