Abstract: Six diet groups containing protein (44%, 48%, 52%) and small peptide (0.05% and 0.1%) were fed to groupers (Epinephelus akaara) to assess the effect on growth performance, digestive enzymes activities, serum biochemical and antioxidant abilities. The diets were named as D1 (44%, 0.05%), D2 (44%, 0.1%), D3 (48%, 0.05%), D4 (48%, 0.1%), D5 (52%, 0.05%) and D6 (52%, 0.1%). Each diet was fed to triplicate groups of fish with 15 fish initial weight (42.16±0.23) g which were randomly sorted into each rearing cubic fiberglass tanks and the experimental last for eight weeks. The results show that there was no effect on weight gain (WG), specific growth rate (SGR), muscle moisture, crude protein and ash contents. As protein level and small peptide concentration increased, the crude fats of grouper muscle, triglyceride (TG) and cholesterol (CHO) decreased (P < 0.05). The activity of pepsin was the highest in Group D2, and the activities of amylase, trypsin and lipase were the highest in Group D1.There were no significant difference among different groups (P > 0.05). The activities of malondialdehyde (MDA) and peroxidase (POD) were not significantly different among different groups (P > 0.05). The result shows that supplementation of small peptide at different protein levels can reduce protein requirement, promote fat metabolism and increase digestive enzymes activities.