Phenanthrene(PHE)is one of PAHs(polycyclic aromatic hydrocarbons)and has toxic effects on aquatic animals after being released into the natural water,and crimson snapper(Lutjanus erythopterus)is one of Osteichthys species and an important link of ecosystem in south China sea.In order to understand the toxic effects and mechanism of PHE on L.erythopterus,an acute semistatic toxic test was carried out,and the oxidative stress relative indicators(activities of SOD and content of MDA in liver and gills,activities of AChE in brain)were investigated with crimson snapper(L.erythropterus)exposed to phenanthrene with different concentration(0,10.0,50.0,250 μg/L)for 96 h.The results showed that 24,48,96 h LC₅₀ values were 4.65,3.46,3.17 mg/L,respectively,and its safe concentration(SC)of PHE on crimson snapper was 0.317 mg/L.After being exposed for 96 h,SOD activities of the liver and gills followed an induced trend with 10.0 μg/L exposured.it was inhibited firstly and then induced with 50.0 μg/L and 250 μg/L in the liver,however it was followed the inhibited-inducedinhibited trend of that in gills.The MDA content in the liver and gills has been increasing with time passing,and this also illustrates that the injury degree rose.AChE activity in brain was induced when crimson snapper exposed to low phenanthrene concentration,however inhibited when exposed to higher concentration and it illustrates that phenanthrene could do harm to neurotransmission in fish brain.It is indicated that PHE has performed a higher toxic effect on L.erythopterus,SOD,AChE activities and MDA contents are probable for being the bio-indicators to the phenanthrene pollution because of their higher sensitivities,and could provide information about monitoring and managing of fishery resources.