Abstract: Objective: To study the current status of anti-coagulation treatment by guideline and the best initial warfarin dose in patients with nonvalvular atrial fibrillation (NVAF) in primary hospital. Methods: Two hundred and fifty-six patients without contraindication to anti-coagulation therapy were enrolled into this study. The status of using warfarin were registered and analyzed. Patients with NVAF who used warfain to anti-coagulation treatment were randomly assigned to two groups according to different initial dose,3.125 mg and 5 mg. The dose of warfarin was adjusted according to international normalized ratio(INR),until INR was stabilized between 2.0 and 3.0 for at least 2 months at the same dose of warfarin. Results: Among two hundred and fifty-six cases with NVAF, only 47 cases(18.4%) were given anti-coagulation treatment by guideline. Of the total 164 cases(64.1%) of high risk group,29 cases (17.7%) were given warfarin. Among 164 patients of high risk group,the ratio of warfarin used in paroxysmal atrial fibrillation was significant lower than persistent atrial fibrillation and long standing atrial fibrillation (P < 0.05). Treatment decision-making of physicians and patients factors were associated with low rates of warfarin used. The mean time achieving a stabilized target INR in two groups was significant(P > 0.05). The incidence of exorbitant INR was shorter than that in the 5 mg group(P < 0.05). There was no significant difference in thromboembolisms and important hemorrhage complications in two groups(P > 0.05). Conclusions: Most of the patients with NVAF did not receive appropriate antithrombotic therapy in primary hospital. An initial warfarin dose of 3.125 mg treatment may reach the stabilized INR range quickly,safely and efficiently without increasing the bleeding complications.