This study aims to investigate the effects of limonin on learning and memory abilities and antioxidant capacity of natural apolexis rats.Methods 18 months male SD rats was used as natural apolexis model, and randomly divided into control group and limonin group (50,0 mg/kg), and then continuous lavage for 6 weeks. At seventh week of the experiment, the learning and memory ability were determined by Morris water maze, and the oxidation and anti-oxidation ability was detected in rat serum and brain tissue. Results Different doses of limonin could reduce the time of reaching the end and the total distance of swimming, the times through original security platform, the original security platform in quadrant activity time and distance in space exploration test were significantly increased, and limonin could reduce MDA and Lipo levels in natural apolexis rats serum and brain tissue, increase the SOD, GSH-Px activities in serum and brain tissue and the ability of T-AOC in brain tissue.Conclusion Limonin could improve the learning and memory ability of natural apolexis rats, improve the antioxidant ability of brain tissue, delay the aging of the brain function.