Purpose: This study was conducted to investigate the muscle anti-fatigue effects of Morindae officinalis Radix liquid extract. Methods: 4-6 weeks old ICR rats are used in the study, and we administered the extracts powder of Morinda officinalis concentration of 1, 10, 100mg/0.3 ml to each to rats(MO group) once a day for each 30 and 60 days. After 30 and 60 days, we examined the plasma concentraion of lactate dehydrogenase, glucose. And we measured the persistent time of swimming exercise test and conducted grip strength test Results: We found that there are no significantly differences between the control and the treatment group in the plasma concentration of activity level of lactate dehydrogenase. And we found that in 30days group, level of glucose concentration is significant. In swimming exercise test, as administration time and concetration growed up, swimming time is increased. And in grip strength test, as concentraion is growed up, grip strength is increased. Conclusion: This study show that Morinda officinalis is effective against muscle fatigue.