Abstract: Perinereis aibuhitensis is used as biological subject in acute toxicity test, for determining the 96 h-LC50 of tetrabromodiphenyl ether(BDE-47).On this basis, the activities of SOD,CAT,GST,GPx and the contents of GSH, MDA of the antioxidant defense system of Perinereis aibuhitensis exposed to 0,2,4,8 mgL-1 of BDE-47 pollutants were determined. The results were as follows:the 96h-LC50 of BDE-47 to Perinereis aibuhitensis was 31.24 mgL-1.Compared with the control group, the content of GSH and activities of GST and CAT had basically no significant change, only the GST activity of 8 mgL-1 group was significantly higher (P0.01) on 14 th day.The GPx activity of 4 mgL-1 group was significantly higher (P0.05) on 1 th day, and 2 mgL-1 group showed the increasing trend during the 7 th to 14 th day.On 1 th day, the SOD activity of the 4 mgL-1and 8 mgL-1 groups significantly decreased (P0.05).Overall, during the period of 1-7 d, SOD activity of the 2 mgL-1, 4 mgL-1groups were induced to rise. On 14 th day, SOD activity in 4 mgL-1, 8 mgL-1 groups were significant (P0.05) and significantly (P0.01) inhibited respectively. The MDA content of all the treatment groups were induced to increase (P0.05), and 4 mgL-1 group significantly increased (P0.01) on 1 th day. There was no significant change in the content of MDA of the treatment groups during the exposure period of 4-14 th day, only 8 mgL-1 group was significantly higher (P0.05) on 7 th day.In conclusion:the content of MDA and activity of SOD of the antioxidant defense system of Perinereis aibuhitensis had significant changes at the early exposure stage (P0.05), which could be used as potential biomarkers.