Objective To investigate the antioxidant effects of polysaccharide extraction from Eupolyphaga sinensis Walker (ESW) in vitro and in vivo. Methods The methods of spectrophotometry, pyrogallol autoxidation and Fe²⁺ phenanthroline were used to detect the free radicals scavenging (DPPH·,O₂^-·and·OH), erythrocyte oxidative hemolysis and liver mitochondrial swelling of polysaccharide extraction from ESW in vitro. The mice were administered with different doses of polysaccharide extraction from ESW (0, 40, 80, 160 mg/kg) for 20 days in vivo. The contents of MDA in different tissues of the mice were determined by TBA method, and spectrophotometry was used to assay the activity of antioxidant enzymes (SOD, CAT, GSH-Px).Results Compared with the control group, free radical (DPPH·, O₂^-·and·OH) scavenging rate was significantly improved with the increasing concentration of polysaccharide extraction. There was a significant decrease in the oxidation hemolysis of erythrocytes and mitochondrial swelling in vitro. MDA contents were decreased in the polysaccharide group, and the activities of SOD, CAT and GSH-Px were significantly higher than those in the control group. Conclusions Polysaccharide extraction from ESW can eliminate free radicals, reduce cell oxidative damage caused by free radicals, inhibit the formation of peroxide in tissues, and increase the activity of antioxidant enzymes, indicating a good antioxidant property.