Atrial fibrillation （AF） as a most frequent arrhythmia has a high incidence of 79% in patients with mitral valve disease. Thrombosis, embolization and serious arrhythmia can be caused by AF. There is the recrudescent tendency in using drugs to recover the sinus rhythm, surgery and radio frequency ablation can only cure a part of patients. By now the pathogenesis of AF is not known clearly. The pathogenesis of AF from virulence gene, cardiac electrophysiology, connecxins, cell ultramicrostructure and cell signaling system are reviewed in this article.