Objective:To explorer the effect of aspirin and warfarin on prevention thrombus of paroxysmal nonvalvular atrial fibrillation(PAF). Methods:Eight hundred and seven patients with PAF were investigated, and divided into four groups. Patients were treated by Aspirin or warfarin. main destination events, secondary destination events, main bleeding events and secondary bleeding events were observed and compared. Results:Compared Aspirin group, on main destination events and secondary destination events were lower in patients with higher of risk PAF(P﹤0.05),but there were no difference on main bleeding events and secondary bleeding events(P > 0.05). Three were no different on main destination events and secondary destination events between group Aspirin and warfarin in moderate risk of PAF patients(P > 0.05),but warfarin could lower secondary destination events and total events compared with Aspirin(P﹤0.05). Conclusion:On PAF patients with higher stoke, warfarin on preventing thrombus superiored aspirin. On PAF patients with medium stoke, there were no difference between warfarin and aspirin on main events and bleeding events, but patients treated by warfarin can reduce secondary destination events.