Objective To explore the role ofmirror image on arterial lesion severity of acute ST segment elevation myocardial infarction (STEMI) patients with electrocardiograrn(ECG) reciprocal lead ST segment,as well as its clinical prognosis.Methods Totally 167 STEMI patients with completed data were enrolled in present study.The patients were divided into four groups according to the amplitude of corresponding lead ST segment.Group Ⅰ consisted of 33 patients with non ST depression and group Ⅱ consisted of 97 patients whose amplitude of corresponding lead ST segment were less or equal to the amplitude of the ST segment elevation in myocardial infarction area.Group Ⅲ consisted of 25 patients whose amplitude of corresponding lead ST segment was larger than the amplitude of the ST segment elevation and group Ⅳconsisted of 12 patients whose corresponding ST segment and ST segment in myocardial infarction area were all elevated.The culprit artery lesion and clinical prognosis were compared between the four groups.Results There were significant differences in terms of the extent of lesion stenosis and the number of coronary artery stenosis among the four groups (x2 =13.49,P＜0.05;x2=78.34,P＜0.01).In Ⅳ group,the prognosis indices included pump failure,low blood pressure,malignant arrhythmia,ventricular wall incoordination,left ventricular ejection fraction ≤ 50％ and inhospital mortality significantly increased(P＜0.01).Conclusion Different corresponding ST segment depression in patients with acute ST segment elevation myocardial infarction can forecast the culprit artery lesion and clinical prognosis.