Abstract: This study was conducted to measure antioxidant capacity of fermented wheat bran polysaccharides(FWBPs) in vitro and its antioxidative potential against diquat-induced oxidative stress of spleen of rats. The reducing power, DPPH radical and hydroxyl radical scavenging rate of FWBPs were determined. Forty-eight healthy weaned Wistar rats were randomly assigned to six groups with 8 rats in each group. The rats in low dose group, middle dose group and high dose group were orally treated with FWBPs at 100, 200 and 400 mg/kg BW, respectively, in positive control group were orally treated with vitamin C at 100 mg/kg BW, in normal group and toxic group were orally treated with equal volume saline for 14 days. After the last gavage for 2 hours, except the normal control group, the other five groups were intraperitoneally injected with diquat(0.1 mmol/kg BW) to establish the oxidative stress model. After challenged 24 h, the spleen tissues were collected to measure antioxidant indices by ELISA kits. The mRNA expression of antioxidant related genes was determined using RT-PCR. The results showed that the saturation scavenging rates of FWBPs to DPPH radical and hydroxylradical reached 92.35% and 33.30%, respectively. Diquat treatment significantly decreased the activities of glutathione peroxidase(GSH-Px)(P<0.05), while increased total antioxidative capacity(T-AOC), 8-hydroxy deoxyguanosine (8-OHdG) contents, and the mRNA expression of glutamate cysteine ligase modifiersubunit(GCLM) in the spleen tissues of rats(P<0.05). Under the oxidative stress, the activities of GSH-Px increased in the low and middle dose group(P<0.05); the glutathione(GSH) contents increased in the low dose group(P<0.05); the mRNA expression of NAD(P)-Hquinoneoxidoreductase 1(NQO1) and nuclear factor E2-related factor 2(Nrf2) increased in the middle dose group(P<0.05); while 8-OHdG contents decreased in the middle, high dose group and positive group(P<0.05). In summary, FWBPs exerted strong antioxidant effect against oxidative stress induced by diquat of spleen in rats.