The anti-fatigue effect of fermented pu-erh tea on mice was investigated. Kun-ming mice were selected and divided into 4 groups: blank control group was fed with 0.9% normal saline, low-dose group, middle-dose group and high-dose group were fed with 0.5 g/kg, 1.0 g/kg, and 2.0 g/kg of fermented Pu-erh tea respectively. In accordance with the body weight of the mice, different amounts of test sample were fed with. The mice were allowed to drink and eat freely. After 30 d, ten mice from each group were selected for the weight-loaded swimming test and recorded the exhaustive swimming time. For other mice, the blood lactic acid(BLA), blood urea nitrogen(BUN), the activity of lactate dehydrogenase(LDH), muscle glycogen(MG) and liver glycogen(LG) were determined. Results showed: Comparing with blank control group, three groups of fermented Pu-erh tea showed a prolonged weight-loaded swimming time. The contents of BLA and BUN were reduced while the activity of LDH was increased. The contents of MG and LG were increased significantly. Among the three fermented Pu-erh tea groups, the high-dose group showed the best effect.