Abstract： Objective To discuss the best drop velocity of recombinant streptokinase for treatment of aetue myocardial infaretion. Methods Two hundred and four patients with acute myocardial infaretion treated by recombinant streptokinase from August 2005 to August 2008 were reviewed. All patients were retrospectively divided into three groups by drop velocity. Results The coronary artery repantency rate in about 30 minutes after the recombinant streptokinase was 91. 18%. But the arrhythmia which mostly appeared about 10 minutes after the medicine was severe. The repantency rate in about 40 minutes was 88.89% and the arrhythmia was appeared about 30 minutes to one hour. But the arrhythmia was provisional and don't need to be treated. The repantncy rate in about 50 minutes was 67.18%, the arrhythmia was appeared about 1 to 2 hours and needed not to be treat. Conclusion The best safe drop velocity of recombinant streptokinase in treatment of acute myocardial infarction is about 40 minutes.