Abstract: AIM To investigate the effect of irisin on fatty acid oxidation in myocytes and its underlying mechanism. METHODS C2C12 myocytes were divided into six groups randomly as follows: vehicle, irisin (20 ng/ml), irisin (200 ng/ml), irisin (2 000 ng/ml) irisin (2 000 ng/ml)+compound C (30 min before irisin, 20 μmol/L), AICAR (an AMPK activator, 10 μmol/L). The phosphorylated and total AMPK and ACC were determined by Western blot and the oxidation of oleate was assayed by analyzing the oxidation products in the media after the cells were labeled with radioactive oleate. RESULTS 1) Compared with the control group, irisin significantly increased fatty acid oxidation (P<0.05) in C2C12 myocytes. 2) Compared with control group, irisin significantly increased phosphorylated AMPK and ACC-β in C2C12 myocytes (P<0.05 or P<0.01). 3) Compound-C (an AMPK inhibitor) inhibited the increase of fatty acid oxidation and phosphorylation of AMPK and ACC-β induced by irisin in C2C12 myocytes (P<0.05 or P<0.01). CONCLUSION Irisin increases fatty acid oxidation in myocytes and skeletal muscle by activating AMPK.