Abstract: AIM:To study the effect of batroxobin on unstable angina pectoris (UAP) in a canine model. METHODS: The left circumflex coronary artery was instrumented with a flow probe, and critical stenosis and arterial wall injury were induced by mechanical clip. Cyclic flow reductions (CFRs) were created in 20 dogs and the efficacy of batroxobin on thrombus formation, antiplatelet aggregation and fibrinogen (FG) degradation was measured. Assessment of prothrombin time (PT), kaolin-activated partial thromboplastin time (APTT) and thrombin time (TT) were observed. Animals were randomly divided into four groups (control group, batroxobin group I, batroxobin group II, eptifibatide group) and each group was comprised of five dogs.The control group was given saline, batroxobin group I and II were given 0.15 and 0.3 BU/kg, respectively. The eptifibatide group was given 0.24 mg/kg. RESULTS: The time of CFRs decreased after batroxobin 0.15 BU/kg administration. The percent of efficacy reached 80% and the percent of absolute inhibition was 40% with (48.5±14.8) min of the time for CFRs absolute disappearance. CFRs decreased by 62.7% and 81.0%, respectively, at 1 h and 2 h time-dependently after batroxobin 0.3 BU/kg administration, with 100% efficacy and 80% absolute inhibition, and the time for CFRs absolute disappearance was (20.7±25.4) min. Batroxobin 0.30 BU/kg inhibited platelet aggregation induced by ADP. FG decreased significantly 1-2 h after batroxobin 0.15 BU/kg administration with degradation of 51.5% and 57.2%, respectively, and batroxobin 0.3 BU/kg produced maximal degragation to about 78.5%. Batroxobin administration exerted no effects on PT but increased APTT and TT. CONCLUSION: Batroxobin has reliable therapeutic efficacy on UAP.