Abstract: Objective To explore the value of 18-lead electrocardiogram(18-lead ECG)in the diagnosis of acute posterior myocardial infarction. Methods Totally 70 patients with acute myocardial infarction were selected. All the patients were conducted with routine ECG and 18-guide ECG examinations, and the diagnostic value was compared. Results According to the results of comprehensive laboratory and imaging examination, there were 28 cases diagnosed as acute posterior myocardial infarction and 42 cases diagnosed as other types of myocardial infarction. The detection rates of 18-lead ECG for acute posterior myocardial infarction and other types of myocardial infarction were 92.86%(26/28)and 95.24%(40/42)respectively, which were significantly higher than 67.86%(19/28)and 71.43%(30/42)by routine ECG(P<0.05). The sensitivity, specificity and accuracy of 18-lead ECG in the diagnosis of acute posterior myocardial infarction were significantly higher than those of routine ECG, and the rate of missed diagnosis and misdiagnosis was significantly lower than that of routine ECG(P<0.05). Compared with patients with other types of acute myocardial infarction, the ratios of cases with slightly decrease of V1 to V3 ST segment, slightly increase of RV1 and slightly increase of V7 to V9 ST segment were significantly higher in those with acute posterior myocardial infarction(P<0.05). Conclusion The 18-lead ECG can be used in the diagnosis of acute posterior myocardial infarction, which should be implemented in combination of the clinical symptoms and the results of myocardial enzyme spectrum detection in order to reduce rate of misdiagnosis and missed diagnosis, and increase the diagnosis rate of the disease.