In this study, we tested anti-fatigue effect of Kyung-Ok-Ko (KOK). We examined the exercise performance effects of KOK (600 mg/kg) at 2nd, 3rd and 4th week. The exercise performance of KOK treated group was significantly improved than that of vehicle control (VC) group on grip strength (2nd week), exhausted time of treadmill (3rd week) and exhausted time of weight loaded swimming (4th week). We also investigated the effects of KOK on the change of fatigue parameters in blood, skeletal muscle and liver after swimming exercise. KOK significantly reduced lactate level and enhanced glucose level in blood. Equally KOK significantly increased glycogen in skeletal muscle. However, the glycogen level of KOK in the liver was not significantly increased compared to VC group. These results show that supplementation of KOK may improve the anti-fatigue activity and exercise capacity.