Objective To study the effect of maca extract on sport fatigue and its antioxidant effect. Methods 50 healthy male Wistar rats were randomly divided into control group (normal breeding, without swimming, equal amount of distilled water for gavage), simple swimming group (swimming, equal amount of distilled water for gavage), swimming and medicine group (divided into maca extract 4.0, 8.0 and 16.0 g/(kg· bw) groups, respectively), 10 rats in each group. All rats were freely swimming in the circulating water flow daily for 15 days. On the 16th day of experiment, liver tissue samples were collected. The liver lipid peroxide (LPO),superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and liver glycogen level were determined. Results When rats were administered with maca extract at the doses of 4.0, 8.0, 16.0 g/(kg· bw), respectively, the swimming time before sinking and the total swimming time were increased by 18.99%, 64.46% and 90.69%, and 18.99%, 56.23% and 94.72%, respectively, while the numbers of times of sinking were decreased by 27.44%, 42.86%, 64.11% (P<0.01), respectively, compared with the swimming rats without maca extract treatment. The LPO content in the liver of rats treated with maca extract 4.0, 8.0, 16.0 g/(kg· bw) were reduced by 31.31%, 42.00% and 31.31%, respectively, while the levels of SOD, GSH-Px and liver glycogen were enhanced by 25.92%, 31.82%, 62.09%, 12.33%, 23.01%, 46.36% and 17.83%,44.69%, 62.99%,respectively, over those of rats without maca extract treatment. Conclusions Maca extract reduces the liver LPO level, increases liver glycogen level, improves the SOD and GSH-Px activity, therefore, plays a protective role in sport fatigue.