From April 2011 to January 2012, we set one section in intertidal zones respectively in seaweed bed coast of Sargassum horneri and out-seaweed bed coast of Huokun'ao, Nanji islands, and surveyed the species and amount of intertidal macrobenthos, species biodiversity and the characteristics of community structure. In this survey, we totally identified 108 species, including 93 species of macrozoobenthos and 15 species of benthic macroalgae. The annual average biomass and abundance of mollusks, arthropods, polychetes, other animals and algae were not significantly different in seaweed bed and out-seaweed bed coast. There was no significant difference in annual average biomass and abundance of mollusks, arthropods, polychetes, other animals and algae of the two sections in high tidal zone and middle tidal zone, but in low tidal zone, the algae biomass of the seaweed bed coast was higher than that of the out-seaweed bed coast, the biomass and abundance of other groups had no significant difference. There was no significant difference in all seasons and all tidal zones in seaweed bed and out-seaweed bed coast, except spring, in which the algae biomass of low tidal zone in seaweed bed coast was higher than that in out-seaweed bed coast. The dominant species of intertidal in seaweed bed coast was Septifer virgatus, in out-seaweed bed coast were Septifer virgatus and Saccostrea echinata. There was no significant difference(P>0.05)in Shannon-Wiener (H'), Pielou (J) and the Margalef (d) in seaweed bed and out-seaweed bed coast. Nonmetric multidimensional scaling (MDS) and cluster analysis showed that the community structure was mainly related with seasons, but during the period when Sargassum horneri grew exuberantly, it was related with the seaweed bed, which suggested that the exuberant growth period of Sargassum horneri would affect the community structure.