Objective To investigate the relationship between left atrial dimension and atrial fibrillation of coronaray heart disease.Methods The coronaray heart disease patients were divided into three groups,non-atrial fibrillation(group 1),paroxysmal atrial fibrillation(group 2),atrial fibrillation(group 3).Results The rate of atrial fibrillation is increased obviously than normal left atrial dimension.Conclusion The rat of atrial fibrillation in larger left atrial dimension is higher.