By changing water salinity gradually and temperature suddenly, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in livers of selective group of Trachinotus ovatus at different salinities (10, 20, 30, 40) and different temperatures (18.0℃, 21.0℃, 24.6℃, 29.0℃, 32.0℃) were studied respectively. At the end of the experiment, in groups with salinity of 10, the activity of enzymes had no significant difference with control groups (P>0.05); in groups with salinity of 20, the activity of SOD was significantly lower than that of control groups (P<0.01). In groups with salinity of 40, the SOD and GPX activities were significantly lower than those of control groups at 120 h (P<0.05), while the CAT activity had no significant difference compared with the control (P<0.05). In groups with temperatures of 18.0℃ and 21.0℃, the activity of SOD was higher than that of control groups at 1, 3, 6, 12, 24 h, while the activity of CAT was significantly higher than that of controls 24 h (P<0.01). At the end of the experiment (24 h),in groups with temperature of 29℃ the activities of SOD and CAT were significantly higher than those in control groups (P<0.05). In groups with temperature of 32.0℃, the activities of SOD and CAT were significantly lower than those of control groups at 5 sampling time points (P<0.05). The results indicate that the change of water salinity and temperature could enhances the antioxidant enzyme activity in T.ovatus liver. The activation can be inhibited when the salinity and temperature vary beyond the tolerance range of the body.