Objective The purpose of this study was to investigate the mechanism of action of polypeptide extracts of Eupolyphaga sinensis Walker ( ESW) against oxidative aging.Methods Mice were intraperitoneally injected D-galac-tose for consecutive 20 days to establish an aging mouse model.The model mice were administered with different doses of ESW polypeptide (0, 40, 80, 160 mg/kg/d).The normal activity, movement and anti-stress ability of the mice were ob-served.The activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-PX) in blood and different tissues and the content of glutathione ( GSH) and malondialdehyde ( MDA) of the aging mice were assessed by xanthin oxidase activity measurement and spectrophotometry, respectively.The expression of nuclear factor erythroid 2-re-lated factor 2 (Nrf2) in Caco-2 cells was detected by immunofluorescence.Results Comparing the control and polypep-tide groups, there were significant decreases of body weight gain, organ indexes, anti-stress ability and activity capacity, the activity of SOD, CAT, GSH-PX and the content of GSH, and an increase of the content of MDA in blood and different tissues in the aging mice.With the increasing dose of polypeptide extracts of ESW, the body weight gain, organ indexes of the liver, spleen and kidney were significantly increased, the static and dynamic exercise time was prolonged in the poly-peptide group, and their abilities of hypoxia tolerance and heat tolerance were close to that of normal controls.The SOD, CAT, GSH-PX activity and GSH level in blood and different tissues were significantly increased, but MDA content de-creased.The expression of Nrf2 in Caco-2 cell nuclei was significantly increased in the polypeptide group, close to that of the positive control group.Conclusions The results of our study show that polypeptide extracts of ESW improve the anti-stress and antioxidative capacity in D-galactose-induced mouse models of oxidative aging by initiating Nrf2-ARE antioxidant signaling pathway, therefore, delay the oxidative aging in mice.