Abstract: To understand the characteristics of macrobenthos community structure in Qinzhou Bay,investigation of macrobenthos was carried out in spring of 2011 and autumn of 2012.The results showed that 31 and 33 species were identified in spring and autumn,respectively.The main species belonged to polychaetes,mollusks and crustaceans.The dominant species was Timoclea imbricata Sowerby both in spring and autumn.The average density was 117.92 ind/m² and 152.50 ind/m² in spring and autumn,respectively,which was higher in autumn than in spring.The average biomass was 63.93 g/m² and 41.20 g/m² in spring and autumn,respectively,which was greater in spring than in autumn.The average biological diversity index was 1.60 and 1.93 in spring and autumn,respectively,which was more in autumn than in spring.The above biological community structure parameters on the spatial distribution were characterized by low in sewage discharge and reclamation areas,which indicated that sewage discharge and reclamation and other human activities have impacted on the community structure of macrobenthos significantly in Qinzhou Bay.The results could provide the basis for ecological environment protection in semi-closed bay.