Abstract: AIM:To investigate the curative effect of metoprolol in prevention and treatment of atrial fibrillation (AF) after coronary artery bypass graft (CABG). METHODS: We retrospectively analyzed the clinical data of 332 CABG patients in our hospital from January 2010 to January 2013. According to the postoperative ventricular rate, patients were divided into group A and group B, with 166 cases in each group. In Group A, the ventricular rate was controlled <70 times/min using adequate metoprolol and in Group B, the ventricular rate was controlled >85 times/min using suitable amount of metoprolol. RESULTS: No significant difference between groups was found in age, body mass index, ejection fraction, extracorporeal circulation time, and endotracheal intubation time (P>0.05). The incidence of AF in Group A was obviously lower than that in group B, with significant difference between groups (P<0.05). CONCLUSION: It is safe and effective to use metoprolol in prevention and treatment of AF after CABG.