Abstract: Objective：To investigate the influencing factors and short-term prognosis of perioperative myocardial infarction (MI) after elective percutaneous coronary intervention (PCI) in patients with acute myocardial infarction. Methods：132 patients who had non-ST-segment elevation myocardial infarction (NSTEMI) or ST-segment elevation myocardial infarction (STEMI), missed coronary revascularization for over half a month and still had symptoms were selected. The patients were divided into 2 groups: perioperative MI group (Group A, n=63) and non-perioperative MI group (Group B, n=69). The basic clinical data of patients in the two groups, blood biochemical examination results, preoperative medication, the results of coronary angiography, coronary artery microcirculation resistance index (IMR), left ventricular end-diastolic dimension (LVEDd) and left ventricular ejection fraction (LVEF) immediately after operation and 3 months postoperatively were compared. Multivariate Logistic regression analysis was used to analyze serum glucose level, q-CRP and IMR. The data of major adverse cardiovascular events (MACE) within three months after PCI were collected. Results：There were significant differences in IMR, q-CRP and blood glucose between the two groups (P<0.05). Multivariate Logistic regression analysis showed that IMR was the factor contributing to perioperative myocardial infarction. IMR had positive correlation with cTnI and its incremental value after PCI (P<0.05). There were significant differences in LVEDd, LVEF, and their increased values 3 months after PCI between the two groups (P<0.05). The incidence of MACE was higher in Group A (28.6%) than that in Group B (10.1%), and the difference was statistically significant (P<0.05). Conclusions：IMR is an important factor for myocardial infarction after PCI. The short-term prognosis of such patients is poor.