Purpose to probe into the anti-fatigue ability of selenium-rich Cordyceps militaris. Research methods: (1) Determination of mycelium components: The polysaccharides, organic selenium and superoxide dismutase of mycelium were measured; (2) Determination of anti-fatigue ability: The mice were treated with different dosages of selenium-rich mycelium per day. Each group was tested separately of the mice’s exhaustive swimming time and the content of blood lactate and blood urea nitrogen. Results: the content of mycelia polysaccharide and the activity of superoxide dismutase (SOD) in Cordyceps militaris enriched selenium mycelia was increased. The mice treated with mid-dosage obviously prolonged the weight loading swimming exhaustive time. The mid-dosage of selenium-rich Cordyceps militaris could prolong or reduce the production of lactate acid, quicken the clearance of lactate acid. Conclusions: The polysaccharides content, organic selenium content and the activity of SOD enzyme in the selenium-rich mycelium powder increased significantly. selenium-rich Cordyceps militaris can increase the anti-fatigue ability of the exercise in the mice.