Abstract: The experiment aimed to investigate the effects of γ-aminobutyric acid and vitamin C supplementation on growth performance and serum biochemical indices of the Magang Goose under heat stress. A total of 240 45-day-old geese were randomly divided into three groups by the weight consistency principle, including a control group （groupⅠ, fed with basal diet）, and two treatment groups （groupⅡ and Ⅲ, fed with basal diet supplemented with 100 mg/kg of γ-aminobutyric acid and vitamin C, respectively）. The results showed that, in the growth performance, supplementation of γ-aminobutyric acid and vitamin C in basil diet significantly increased the daily weight gain （DWG, P〈0.05） and daily feed intake （DFI, P〈0.05）, and significantly decreased the ratio of DFI to DWG （P〈0.05） comparing with control group, while the vitamin C group had higher DWG （P〈0.05） and lower ratio of DFI to DWG （P〈0.05） compared with the γ-aminobutyric acid group. In serum biochemical indices, supplementation of γ-aminobutyric acid and vitamin C in basil diet significantly decreased the activities of serum LDH, GOT, GPT, AKP and contents of serum MDA and BUN（P〈0.05）, and significantly increased the activities of serum SOD, T-AOC and concentrations of serum TP and T3 （P〈0.05） comparing with control group. There was no difference on the activity of GSH-Px and T4 level between treatment groups and control group （P〉0.05）. These results demonstrated that dietary supplementation of γ-aminobutyric acid and vitamin C could improve the growth performance, activities of SOD and T-AOC; decreased the content of MDA, activities of LDH, GOT, GPT and AKP; and promoted the secretion of T3 of the Magang Goose under heat stress.