Objective To study tirofiban intravenous injection,coronary artery injection of the two different methods in acute ST segment elevation myocardial infarction,the application of emergency PCI.Methods Patients underwent emergency PCI with acute ST segment elevation myocardial infarction as the research subjects,a total of 108 cases,the patients were randomly divided into the observation group and control group,54 patients in each group. In the observation group,the first dose of tirofiban was injected into the coronary artery.The control group was treated by intravenous injection.The results of the two groups were compared.Results Before treatment,TIMI level 2 and level 3 ratio,initial corrected TIMI frame count of the observation group were significantly lower than the control group (χ2 /t =4.32,4.59,5.25,all P <0.05).After treatment,MBG level 2 or level 3 ratio,post -operative corrected TIMI frame count of the observation group were significantly higher than the control group (χ2 /t =4.11,4.85,5.87, all P <0.05).1 h after PCI treatment,the number of cases of ST fully back,the added value of EF,plague index scores of observation group were 53 cases,(8.02 ±6.94)%,(0.41 ±0.28)respectively,which were significantly higher than those of the control group 36 cases,(5.87 ±6.54)%,(0.28 ±0.27)(χ2 /t =5.32,4.32,3.65,all P <0.05).Adverse events of the two groups had no significant difference (χ2 =0.52,P >0.05).Conclusion Compared with intravenous injection,tirofiban in the treatment of acute ST segment elevation myocardial infarction by intracoronary injection can improve the level of myocardial perfusion after PCI operation,promote the recovery of left ventricular function,and has high security.