Nianmianzi is a unique fermented food in Northeast China which is fermented with corn flour as raw material. In order to explore whether Lactiplantibacillus plantarum H8 isolated from Nianmianzi can improve the oxidative damage in mice, an aging mouse model of oxidative damage induced by D-galactose was established, and its possible signal mechanism was studied. 32 Kunming mice were injected with 200mg/kg D-galactose every day to induce oxidative damage in mice, and at the same time, Lactiplantibacillus plantarum H8 with a concentration of 1.0×10¹⁰CFU/mL was gavaged for 8 weeks to observe the effect of H8 on serum and liver of mice with oxidative damage. According to the findings, H8 could prevent oxidative stress in mice tissues by raising the organ index. It could also dramatically lower oxidative stress levels in serum and liver, including NO and MDA, and increase the activity of antioxidant indices in serum and liver, like SOD, GSH-Px, and GSH. Furthermore, Lactiplantibacillus plantarum H8 was shown to be able to lessen the harm that D-galactose caused to mice's liver, spleen, brain, and colon tissue using H&E section staining. Meanwhile, Lactiplantibacillus plantarum H8 had the ability to promote the expression of antioxidant enzymes generated by the Nrf2-ARE pathway at the mRNA and protein levels, as well as activate sirtuins 1 (SIRT1) and sirtuins 3. SIRT1 could encourage the ubiquitination and destruction of p53 and lessen the production of reactive oxygen species. The findings suggested that the up-regulation of the SIRT1/SIRT3/Nrf2 signaling pathway might be connected to the antioxidant activity of Lactiplantibacillus plantarum H8, and a possible correlation between the SIRT3 signaling pathway and Lactiplantibacillus was investigated. The goal of this study wa to provide theoretical reference for developing antioxidant probiotic products.