Abstract: Objective: To observe the anticoagulant effect of warfarin in the treatment of elderly patients with type 2 diabetes complicated with atrial fibrillation.Methods: One hundred and thirty-two diabetic patients complicated with atrial fibrillation with the age over 75 were divided into warfarin moderate intensity groupinternational normalized ratio(INR) was maintained at 2.1-2.5,warfarin low intensity group INR was maintained at 1.5-2.0 and control group(aspirin),each group consisting of 44 cases.All the cases were followed up for 1 year.The incidence of thromboembolism and bleeding events were recorded.Results: The incidence of thromboembolic events tended to increase in the moderate intensity group,low intensity group and control group;the incidence of thromboembolism in the control group was higher than that in the warfarin moderate intensity group and low intensity group(P<0.05);the difference in the thrombembolia rate had no statistical significance between the moderate intensity group and the low intensity group(P>0.05).The bleeding events tended to reduce in the moderate intensity group,low intensity group and control group;the bleeding rate of the moderate intensity group was higher than that of the low intensity group and the control group(P<0.05);but the bleeding rate in the control group had no statistical significance compared with that in the low intensity group(P>0.05).Conclusions: warfarin is effective on senile diabetic patients complicated with atrial fibrillation when the INR value is maintained at 1.5-2.0,which may achieve the best anticoagulant effect and avoid the occurrence of bleeding events.