Abstract: The SOD activity and MDA content in mantle were studied after Perna viridis exposing to different concentrations (2.0 μg · L^-1, 10.0 μg · L^-1 and 50.0 μg · L^-1) of phenanthrene (PHE)and benzo (b) fluoranthene (BbF) separately under experimental conditions. The results indicate that the SOD activity follows an induced-inhibited trend with phenanthrene exposure, and it is significantly induced by exposure to benzo (b) fluoranthene at 15^th day(P < 0.05).The change in MDA content suggests both PHE and BbF exposure may cause oxidative damage to the mantle, but in clean water, the damage is ameliorated gradually until it returns to normal. Since SOD activity and MDA content in the mantle of P.viridis change obviously and differently with 2 kinds of PAHs exposure, the biochemical indicators for P.viridis are suitable to indicate the pollution to the marine environment by PAHs.