Abstract: Objective To investigate the relationship between myocardial ischemia grading diagnosed by electrocardiogram and target vessel location as well as stenosis in patients with acute myocardial infarction(AMI). Methods A total of 100 AMI patients were selected as research objects, and were divided into two groups. Fifty patients with grade 2 myocardial ischemia were selected as grade 2 myocardial ischemia group, another fifty patients with grade 3 ischemia were selected as grade 3 myocardial ischemia group. Clinical relevant indicators, target vessel position, degree of stenosis were compared, and major adverse cardiovascular events after 6-month follow-up of two groups was recorded. Results The baseline values and increase degree of serum creatine kinase isoenzyme(CK-MB), brain natriuretic peptide(BNP)and the of cardiac troponin I(cTnI)in the grade 3 myocardial ischemia group were significantly higher than those in the grade 2 myocardial ischemia group(P<0.05); the proportions of patients with left anterior descending branch lesion, more than one target lesion, and entire luminal stenosis in the grade 3 myocardial ischemia group were significantly higher, and proportions of patients with left circumflex artery lesion and right coronary artery lesion were significantly lower than those in the grade 2 myocardial ischemia group(P<0.05); the incidence of major cardiovascular adverse events in the grade 3 myocardial ischemia group was significantly higher than that in the grade 2 myocardial ischemia group(26.00% vs. 8.00%, P<0.05). Conclusion There are significant differences in cTnI, CK-MB, BNP, target vessel location as well - as stenosis degree between grade 3 myocardial ischemia and grade 2 myocardial ischemia patients. Myocardial ischemia grading diagnosed by electrocardiogram can provide a powerful reference for physicians to evaluate the location and stenosis of target vessels in patients with AMI.