Hippocampus has long been used as an ingredient in Chinese traditional medical p rescriptions. To explore the health protection effect of hippocampus, four group s of NIH mice were given enzymatic extract of hippocampus (EEH) 0, 50, 100, 200 mg/kg BW respectively by gavage daily for 14 days. On the 14th day, 1 hour afte r the last dose was given, the animals' capacity to tolerate fatigue was tested by physical exercise (swimming) of various intensity. The level of blood lactic acid, serum urea nitrogen and lipid-peroxidation of skeletal muscle of hind le g were used as indexes of the capacity of tolerance. The results showed that the rise of these indexes was significantly lower and their clearance was faster af ter swimming in animals received EEH than those in the animals of the control gr oup. It was also observed that the anti-fatigue action of EEH was dose-depende nt, the larger the dose the stronger the action. Furthermore, EEH's effect was also related to the physical condition of the animal. The anti-fatigue effect enhanced with the increase of the intensity of physical exercise. In an addition al test,EEH was found to have the effect of withstanding hypoxia and coldness.