OBJECTIVE: To explore the effect of different starting time of thrombolysis on acute myocardial infarction (AMI). METHODS: Ninety-five patients of AMI were divided into prompt thrombolysis group (less then 6 h, 46 patients) and delayed thrombolysis group (6-12 hours, 49 patients), according to the different starting time of treating AMI. The incidences of reopening and side-effect, as well as mortality were compared between two groups. RESULTS: The reopening rate and mortality in prompt thrombolysis group were 76% and 4%, respectively. The reopening rate and mortality in delayed thrombolysis group were 49% and 12%, respectively. Compared the prompt thrombolysis group with the delayed thrombolysis group, there was a significance discrepancy (both P<0.01). The side-effect rate had not significant discrepancy (15% vs. 16%, P>0.05). CONCLUSION: The clinical reopening rate of the thrombolysis is higher in patients with thrombolysis less than 6 hours, the mortality is lower. The thrombolytic treatment should be prompt for patients adapting thrombolysis.