Objective To observe the efficacy and safety of warfarin in long-time anticoagulation treatment in elderly patients with nonvalvular atrial fibrillation (NVAF).Methods NVAF patients were divided into 3 groups according to their ages: advanced elderly group [n=55, age≥80, and international normalized ratio (INR) controlled from l.6 to 2.5], elderly group (n=45, aged from 65 to 79, and INR controlled from l.6 to 2.5) and middle-aged group (n=37, age<65, and INR controlled from 2.0 to 3.0). All enclosed patients were given warfarin for anticoagulation treatment for a long time, and the dosage of warfarin was adjusted according to INR detection values and change trends. The adverse reactions, safe range and INR of warfarin for 5 y were compared in 3 groups.Results During 5-year follow-up period, there was no ischemia stroke observed, and there was no statistical difference in bleeding and other adverse reactions in 3 groups (P>0.05). On the 5th year, dosage of warfarin was (2.89±0.52) mg and INR was (2.15±0.31) in advanced elderly group, and (2.99±0.41) mg and (2.21±0.30) in elderly group without statistical difference (P>0.05). In middle-aged group, the dosage of warfarin was (3.39±0.61) mg and INR was (2.55±0.60), which was significantly higher than those in advanced elderly group and elderly group (P<0.05). Conclusion When warfarin is used for anticoagulation treatment effectively and safely in elderly patients with NVAF, INR should be closely monitored and controlled from 1.5 to 2.5.