This study is a comparative analysis of the best timing for applying tirofiban in the PCI emergency treatment for STEMI patients. We selected 109 patients with ST-segment elevation myocardial infarction from October 2013 to October 2014 and divided them into two groups, the early treatment group (53 cases) received tirofiban during the operation and the later treatment group (56 cases) received tirofiban after operation. The analysis was then conducted. Results: The proportion of IRA forward flow in TIMI2-3 for the 1st group during the radiography was higher than 2nd group, 50 cases with TIMI3 blood flow and 52 cases with TIMI3 blood flow in later treatment group. Comparing the TIMI3 flow of both groups, the difference was not statistically significant; for the CK-MB 4h and 8h after operation as well as the LVEF after operation, the differences are were not statistically significant. The occurrence rate of hemorrhage complication was low for both groups. The early use of tirofiban can make the thrombus fully dissolve and coronary blood flow remains in a good state, which is not only beneficial for myocardial perfusion but also helpful for deciding the length and side branch situation of coronary artery pathological changes.