The effects of different dissolved oxygen (DO) concentrations, including severe hypoxia(0.2, 1.0, 2.0 mg/L), hypoxia(3.0, 5.0 mg/L), normoxia(normal aeration as control, about 7.0 mg/L) and hyperoxia(11.0, 14.0 mg/L), on nucleus anomaly in erythrocytes, superoxide dismutase(SOD), catalase(CAT) activities in serum and malondialdehyde(MDA) concentration in liver were studied in juvenile turbot Scophthalmus maximus. Fish mortality was only observed in the 0.2, 1.0 and 2.0 mg/L groups, in which all fish died in 2 h, 24 h and 48 h, respectively. The effects of DO on nucleus anomalies were shown with obvious timecumulative effects and dosecumulative effects in the 28day experiment. The micronuclei were first observed in the 5.0, 14.0 mg/L and control groups on day 28. They were still found in hyperoxia and control groups after recovery for 14 days. The SOD activities in different groups showed significant difference at each sampling time (P<0.05). The difference in CAT activities among experiment groups was significant only after 7day exposure (P<0.05). The MDA concentration increased with the increasing concentration at 2 h. The MDA concentration in hypoxia and hyperoxia groups decreased with time duration. After 14day recovery, the MDA concentration in hypoxia groups was significantly higher compared with those in control groups (P<0.05). Additionally, the oxidative stresses were also found in control groups. No obvious changes on the total nucleus anomalies and other antioxidative index were found in 5.0 mg/L groups.