The carotenoid crocetin has been shown to relieve the hypoxic condition caused by many diseases. Since hypoxia is also a limiting factor in endurance performance, this study evaluated the effect of crocetin administration on exercise endurance. Eleven treadmill trained rats were randomly divided into an experimental or control group. Sixty minutes prior to exhaustive exercise, the exercise group received a 0.3 mL intraperitoneal injection of 0.2 mg crocetin/kg body weight, and the control group received a placebo injection. The experimental group improved running time by 18±3 minutes (ttest, p≤0.01) and showed a reduction in postexercise blood lactate concentration by 1.84±0.52 mM(ttest, p≤0.01). The results demonstrate that crocetin increased exercise endurance and decreased blood lactate concentration in trained rats. The mechanism of action may be that, by increasing oxygen diffusion, crocetin enhanced aerobic production of adenosine triphosphate while reducing anaerobic adenosine triphosphate production during exercise.