By analyzing 297 stomach contents of Sebastisous marmoratus in seaweed bed around Gouqi Island in April，May, June 2008 and August 2007, this paper studied the feeding habits of this species and its diet composition that varied with seaweed growth. Results showed that feeding intensity was low throughout the study period and percentage of empty stomachs and mean stomach fullness index varied significantly(P<0.05). Percentage of empty stomach varied insignificantly among the size classes(P>0.05). The mean stomach fullness varied insignificantly among specimens less than 80.0mm TL(P>0.05). S.marmoratus was benthivorous and the diet of it consisted of at least 29 different prey species belonging to 12 major groups(Amphipoda, Shrimps, Crabs, Echinodermata, Polychaeta, etc.). Amphipoda were the most important prey and accounted for 97.03% by %IRI of all the prey. The composition of the prey varied with different growth periods of seaweed bed and S. marmoratus size classes. Shrimps and crabs were more important during booming period and flourish period, whereas amphipods were more important during lasting peroid and decay period. Amphipoda were more important in the diet of specimens less than 80.0 mm TL, shrimps and crabs were more important in the diet of specimens 80.0-99.9 mm TL, whereas fish and amphipods occurred more in the diet of specimens less than 100.0 mm TL.