Vitamin E (VE) plays a key role in reproduction,metabolism,antioxidant function and immunity of fish.For the research of effects of dietary VE on tolerance of Epinephelus moara for low salinity stress,five levels of VE supplementation were designed as 0,20,40,80 and 160 mg/kg (A,B,C,D,E in turn) in this experiment.Juvenile E.moara were fed for 56 days,and the real supplementation of VE was tested.Then,low salinity (12) stress experiment lasted for 6 h,different indexes of experimental fish were tested,serum biochemical indexes:cortisol (COR),glucose (GLU),lactic acid (LD);serum antioxidant:superoxide dismutase (SOD),catalase (CAT),glutathione peroxidase (GSH-Px) activities,total antioxidant capacity (T-AOC) and malondialdehyde (MDA);as well as gill Na⁺/K⁺-ATPase (NKA),Ca²⁺-ATPase activities.The results showed that serum COR concentration was increased by supplementing VE in diet.And after low salinity stress,serum COR concentration in every groups increased.There was no huge difference among serum GLU concentration in different groups.And after low salinity stress,serum GLU concentration in groups A,B,C increased significantly.Serum LD concentration in groups C,D,E increased in feeding experiment,then it increased in groups A,B and decreased in groups C,D,E after low salinity stress.Maximum of serum COR concentration was after stress A (32.74±1.53) ng/mL,minimum was before stress E(19.06±3.88) ng/mL;maximum of GLU concentration was after stress A (16.46±0.99) mmol/L,minimum was before culture O (7.90±0.34) mmol/L;maximum of LD concentration was before stress C(1.94±0.15) mmol/L,minimum was after stress E(1.30±0.06) mmol/L.The results of serum COR,GLU,and LD suggested that supplementation of VE would enhance anti-stress ability of E.moara,and the best range of supplementation of VE was 47.524-134.566 mg/kg (B-D).Maximum of SOD activity was before stress C (105.29±9.07) U/mL,minimum was after stress A(11.23±2.30) U/mL;maximum of CAT was before culture O (4.09±0.17) U/mL,minimum was after stress A (0.35±0.10) U/mL;maximum of GSH-Px was before stress E (972.58±55.35) U,minimum was after stress A (47.90±10.64)U;minimum of MDA was before stress D(33.48±2.34) nmol/mL,maximum was after stress A (101.79±7.79) nmol/mL.The supplementation of VE were close relative to serum SOD,CAT,and GSH-Px activities,T-AOC,MDA concentration,of which range was 91.378-178.924 mg/kg (C-E) that could strengthen antioxidant function of E.moara.VE can enhance the NKA activity.When the supplementation of VE was 91.378 mg/kg (C),low salinity stress had little effect on NKA activity.The range of supplementary VE which was 91.378-178.924 mg/kg (C-E),appeared to result in the activation of the Ca²⁺-ATPase activity.This study suggested that diets supplemented with VE can enhance vitality and anti-stress ability of body.In summary,analysis of biochemical,antioxidant and ion-regulatory indicators estimated that the best range of supplementation of VE was 91.378-134.566 mg/kg (C-D).