To develop safe and new anticoagulation agents from natural resources, the inhibitory activities of 291 methanol extracts, which were prepared from different parts of 197 medicinal and wild plants, against human thrombin were evaluated. Based in anti-coagulation activity determined by thrombin time and activated partial thromboplastin time, the extract of leaf of Myrica rubra was finally selected. The extract of M. rubra showed a strong thrombin inhibitory activity (above 1,819%) at 0.5 mg/ml as a final concentration, whereas aspirin showed 337% inhibition at concentration of 1.5 mg/ml. The activity of the extract remained more than 85% and 60% by heat treatment at $100^{circ}C$ for 30min, and acid treatment at pH 2 for 60 min, respectively. Our results suggested that the extract of Myrica rubra could be the potential source as thrombin inhibitor.