Serum biochemical parameters were investigated in juvenile Epinephelus septemfasciatus (300 ± 20 g) subjected to low-temperature stress. The experimental fish at a temperature of 12.4 ℃ were directly shifted to a lower temperature seawater (8.0 ℃) for 0, 1, 2, 5, 10 days. The results showed that, the activity of serum AKP showed an irregular variation trend as a result of low temperature stress, and was significantly higher than that in cold water at 2 days. Enzyme activity of GGT showed a parabolic trend with the maximum efficiency in cold water for 2 days, and minimum for 10days. Glutamate-oxaloacetate (GOT) and glutamyl-transpeptidase (GPT) were increased with the increasing stress duration, and the activities of GOT and GPT at low temperature were significantly higher than those in control group. Enzyme activities of LDH showed insignificant change during the experimental duration. The concentration of serum total protein (TP) showed a descending trend. There was a slight change in concentration of GLU during the prophase of experiment, while the concentration of GLU exposed to low temperature stress at 10 days was 3.9 times high than that in the control group. The concentration of serum TG decreased at earlier stage and mounted at the end of experiment, and no significant difference in TG concentration was found between the initial and end of experiment. CREA concentration showed a similar trend with the TP concentration, declined to 22% of original concentration (48.57±34.96 mmol/L). During the whole experimental duration, no significant difference was found in serum ionic density. In conclusion, juvenile fish with similar size in this experiment can withstand sudden low-temperature change stress and the stress has cumulate effects on juvenile Epinephelus septemfasciatus, indicating that during winter the time of fish kept at 8 ℃ should not exceed 10 days in practice.