Objective To explore factors associated with the quality of warfarin anticoagulation, and the relationship between quality of warfarin anticoagulation and adverse events in patients with atrial fibrillation. Methods Totally, 251 patients with atrial fibrillation （AF） on warfarin therapy were followed up, and data such as international normalized ratios （INRs） and adverse events including bleeding, embolism and deaths were collected during follow-up. Quality of warfarin anticoagulation was reflected as time in therapeutic range （TTR）. Results The included patients had an average TTR of 32.4%, and only 12.0% enjoyed a high quality of warfarin anticoagulation （TTR≥65%）. Logistic regression analysis showed that, age＜60 years （OR=2.911） and previous stroke (OR=5.608） were associated with poor quality of warfarin anticoagulation.The incidence rates of adverse events had no significant differences between the high quality and low quality groups. However, all types of adverse events occurred in the low quality group. Conclusion The quality of warfarin anticoagulation in patients with AF was poor,being far below an effective anticoagulation level.To improve the quality of warfarin anticoagulation and reduce the incidence rates of adverse events, medical staffs should strengthen management of anticoagulation for patients under 60 years of age, those with previous stroke and those with TTR＜65%.