To study the effects of Fomes officinalis Ames. polysaccharides(FOPS) on anti-fatigue and hypoxia tolerance in mice.Forty-eight mice were randomly divided into control group, low-dose, middle-dose and high-dose group of FOPS (100, 200, 400 mg/kg). All mice were orally administered by 0.20 ml/10 g, once a day for 21 consecutive days. The effects of different doses of FOPS on the loaded-swimming time, the content of serum urea nitrogen, the blood lactic acid, the hepatic glycogen and the muscle glycogen after exercise, the survival time under hypoxia at normal pressure and the maintenance time after decapitation were observed.FOPS could significantly prolong the loaded-swimming time, decrease the contents of serum urea nitrogen , blood lactic acid and increase the contents of hepatic glycogen and muscle glycogen, significantly prolong the survival time under hypoxia and the maintenance time after decapitation comparing with the control group. Compared with the control group, FOPS could prolong the weight-bearing swimming time, anti-hypoxia survival time and respiratory maintenance time of mice after decapitation in a dose-dependent manner (P<0.05 or 0.01). FOPS could decrease the contents of serum urea nitrogen and blood lactic acid, and increase the contents of hepatic glycogen and muscle glycogen in exercise mice, and most of them were significantly different (P<0.05) or extremely significant (P<0.01).FOPS has anti-fatigue effects and can improve hypoxia tolerance.