Abstract: In order to study the antioxidative effect of peach gum polysaccharide in vitro and in vivo, this experiment determined the removal rates of 1, 1-diphenyl-2-trinitrophenylhydrazine free radicals (DPPH·), 2, 2-diazo-bis (3-ethyl-benzothiazo-6-sulfonic acid) diammonium salt free cation (ABTS⁺·), hydroxyl radical (·OH) and superoxide anion (O₂^-·) and reduction ability of iron in vitro. An oxidative damage model of D-galactose mice was established, and different doses (2, 4, 6 g/kg) of polysaccharide of peach gum were injected into the stomach. The content of MDA and the activities of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activity in serum and liver were determined. The results showed that the 50% inhibition concentration (IC₅₀) of DPPH·, ABTS⁺·,·OH and O₂^-·in vitro were 6.95, 0.56, 1.10, and 0.11 mg/mL, respectively. And the resistance to iron increased with the increase of the concentration (0.02~0.14 mg/mL).In vivo, compared with the model group, continuous administration of different doses (2, 4, 6 g/kg) of peach gum polysaccharide could significantly or extremely significantly reduce the MDA content in the serum and liver of mice, improve T-AOC ability, and enhance the activity of SOD and GSH-Px (P<0.05 or P<0.01). At the same time, there was a certain quantitative effect relationship between doses. The results show that polysaccharide from peach gum has good antioxidant activity in vivo and in vitro, and can be used as a new antioxidant and free radical scavenger.