Atrial fibrillation (AF) is a common arrhythmia, its incidence increases with age. Thrombosis shed off caused by AF is one of the major causes of stroke. Most patients with AF suffer ischemic stroke that the thrombosis was from the left atrial appendage(LAA). The majority of patients with atrial fibrillation, the blood clots come from the left atrial appendage, so close the left atrial appendage can reduce cycle thromboembolism of the patients with AF. Now patients have cardiac surgery and risk at left atrium related thromboembolism, the surgery has been conventional perform the left atrial appendage closed surgery.