Purpose To investigate the effect of Cordyceps sinensis mycelium on physical fatigue.Methods Cordyceps sinensis mycelium was administered daily at four different doses(125,250,750 mg/kg) to male ICR mice for 30 days.Then were measured the loaded-swimming time,blood lactic acid,hepatic glycogen and urea nitrogen after exercise.Results Cordyceps sinensis mycelium can significantly extend the loaded-swimming time(P0.05),increase the role of reserve in hepatic glycogen(P0.01),reduceing blood lactic acid concentration after exercise in mice(P0.01),and without significant effect on blood urea nitrogen in fatigue mice(P0.05).Conclusion Cordyceps sinensis mycelium can mitigate physical fatigue.