Abstract: AIM:To study the optimal international normalized ratio (INR) of warfarin anticoagulant therapy after mechanical heart valve replacement and to explore its relationship with the adverse events in China. METHODS: A long-term (6-48 months) follow-up of compliance was conducted in 1 684 patients (793 males and 891 females) who received warfarin anticoagulant therapy after mechanical heart valve prostheses from December 2007 to September 2011. The patients ［aged 18-69 years, average age (44.5±18.2) years］ were divided into three groups (AVR/462, MVR/684 or DVR/538) according to different valve prostheses. Each group was divided into four subgroups according to their INR levels (1.4-1.7, 1.7-2.0, 2.0-2.3 and 2.3-2.6). Patients with atrial fibrillation or thrombosis comprised respectively, 302 Cases and 73 cases before surgery. The occurrences of bleeding and thrombosis in these subgroups were compared. RESULTS: In AVR group, bleeding incidences in the subgroups with the INR levels at 1.4-1.7 and 1.7-2.0 decreased significantly compared with those in the subgroups with INR levels at 2.0-2.3 and 2.3-2.6. In the MVR and DVR groups, bleeding incidences in the subgroups with the INR levels at 1.4-1.7, 1.7-2.0 and 2.0-2.3 were lower than those in the 2.3-2.6 subgroup. However, no significant difference was observed in the incidence of thrombosis in all subgroups with different INR levels. CONCLUSION: The results of this study suggest that, in AVR patients, the incidence of bleeding and thrombosis was significantly lower in patients with the INR level at 1.4-2.0 than in patients with INR levels at 2.0-2.6. In MVR and DVR patients, the incidence of bleeding and thrombosis was lower in patients with INR levels at 1.4-1.7, 1.7-2.0 and 2.0-2.3 than in patients with INR levels at 2.3-2.6. Hence, after MVR and DVR, the appropriate level of INR of anticoagulation therapy should remain at 1.4-2.3.