Objective To compare the efficacies and safety of warfarin with different anticoagulation intensities in treatment of nonvalvular atrial fibrillation. Methods Cochrane Library, EMbase, PubMed, Chinese Journal Full-text Database (CNKI), Wanfang Data and VIP Database (VIP) were searched by computer for randomized controlled trials of warfarin with different anticoagulation intensities in treatment of nonvalvular atrial fibrillation. The analysis was performed using the Review Manager 5.3. Results Finally a total of 14 literatures involving 3 295 participants were included. The results of meta-analysis showed the following:low anticoagulation intensity group (INR: 1.5-2.0, n=1 403) had a total bleeding rate significantly lower than the standard anticoagulation intensity group (INR: 2.0-3.0, n=1 892) (RR=0.47, 95%CI: 0.37-0.59, P<0.000 01); there were no significant differences in the incidence of thromboembolism (RR=1.35, 95%CI: 1.00-1.84, P=0.05), ischemic stroke (RR=1.44, 95%CI: 1.01-2.05, P=0.05) or mortality (RR=1.06, 95% CI: 0.85-1.31, P=0.60) between the two groups. Conclusion Warfarin therapy in international normalized ratio of 1.5-2.0 can reduce the risk of fatal and severe bleeding in patients with nonvalvular atrial fibrillation, and may not increase the incidence of thromboembolism.