Objective：This study aims to investigate whether the addition of niacin（NA）to in vitro maturation（IVM）cultures can improve the quality of oocytes derived from aged mice and its mechanism. Methods：C57BL/6J mice at 8 weeks of age were used as the young control group，and mice at 40 weeks of age were used as the old group. Oocytes at the germinal vesicle（GV）stage were taken and supplemented with 100，200，and 300 μmol/L NA，respectively，and the rates of 2-cell and blastocyst formation were observed to determine the optimal concentration. Oocyte quality was assessed by the first polar body extrusion（PBE）rate，cortical granule（CG） distribution，spindle morphology abnormality rate and chromosomal abnormality rate. Mitochondrial function was assessed by mitochondrial membrane potential and adenosine triphosphate（ATP）levels. Oxidative stress levels were assessed by detecting the levels of reactive oxygen species（ROS）in oocytes and mitochondria. The levels of oxidative stress-related proteins：silent information regulator 3（SIRT3），superoxide dismutase（SOD2），and acetylated superoxide dismutase（Ac-SOD2）were detected by Western blot. Results：Under the concentration of 200 μmol/L NA culture medium，the blastocyst formation rate of oocytes in the old +NA group reached its highest level（P ＜ 0.05），therefore this concentration was selected as the optimal concentration. NA supplementation significantly improved the PBE rate and CG distribution in oocytes，while reducing abnormal spindle rates and chromosomal aberration rates，compared with that of the aged mice. NA supplementation also increased mitochondrial membrane potential，enhanced ATP production，and reduced ROS levels in both oocytes and mitochondria（all P ＜ 0.05）. Western blot analysis demonstrated that NA supplementation significantly increased SIRT3 and SOD2 protein expression（all P ＜ 0.05），while markedly decreasing Ac - SOD2 protein expression（P ＜ 0.05）. Conclusion：Addition of 200 μmol/L NA to IVM culture medium improves oocyte quality in aged mice by ameliorating mitochondrial oxidative stress and may act by affecting the SIRT3-SOD2 signaling pathway.