This study was conducted to induce muscle loss using dexametasone and then use the extract to determine its effectiveness in a muscle loss animal model.Animal experimental groups were divided by five groups.Changes in the weight of the animals were measured for a total of 5 weeks.After animal sacrifice, muscle mass was measured, and animal behavior evaluation was conducted using grip strength test and pole test.The expression levels of MAFbx protein was measured using muscle samples.Oral administration of Fomes fomentarius extract was effective in suppressing muscle atropy and increasing muscle, which was confirmed through animal behavior evaluation and muscle-related protein expression.