Objective To evaluate the efficacy of preoperative low-dose oral amiodarone for the prevention of atrial fibrillation （AF） after off-pump coronary artery bypass grafting （OPCAB） in patients older than 70 years. Methods A total of 156 patients older than 70 years who underwent OPCAB in Qingdao Fuwai Cardiovascular Disease Hospital from January 2011 to June 2012 were included in this prospective，double-blind and placebo controlled study. Preoperatively，all the 156 patients were randomly divided into amiodarone group and control group. In the amiodarone group，there were 80 patients including 38 male and 42 female patients who were given oral amiodarone （trade name： Cordarone） 200 mg，three times a day，3-5 days before surgery，and amiodarone was stopped on the OPCAB day and postoperatively. Preoperative duration of amiodarone intake was 4.0±1.2 days，and total amiodarone dosage was 2.6±0.5 g. In the control group，there were 76 patients including 35 male and 41 female patients who were given oral placebo as the same medication schedule，and preoperative duration of placebo intake was 4.0±1.4 days. Operation time，graft number，postoperative AF incidence，AF duration，hospital stay and readmission rate for cardiovascular events within 6 postoperative months were compared between the two groups. Results There was no in-hospital death in either group. There was no statistical difference in graft number，operation time，AF duration of patients who had postoperative AF，or postoperative hospital stay between the two groups. Postoperative AF incidence of the amiodarone group was significantly lower than that of the control group ［18.7% （15/80） vs. 34.2% （26/76），P=0.028］. Seventy-three patients in the amiodarone group （91.3%） and 66 patients in the control group （86.8%） were followed up for 8-24 months. During follow-up，2 patients in the amiodarone group died of acute myocardial infarction and cerebral hemorrhage respectively. There was no statistical difference in readmission rate for cardiovascular events within 6 postoperative months between the 2 groups ［6.8% （5/73） vs. 6.1% （4/66），P=0.860］ .Conclusion Preoperative low-dose oral amiodarone can significantly reduce the incidence of postoperative AF in patients older than 70 years undergoing OPCAB.