Aim To study the significance of T wave shape of aVR lead in predicting left ventricular function in patients with acute coronary syndrome (ACS) with three-vessel disease. Methods 160 patients with ACS three-vessel disease confirmed by coronary angiography were enrolled and divided into T-wave upright group (n＝72) and T-wave inversion group (n＝88) according to the T-wave morphology in lead aVR of electrocardiogram. The general data, left ventricular function, coronary artery lesion and clinical outcome were compared between the two groups. Results Ejection fraction (LVEF) was lower but proportion of LVEF ＜50%, serum N-terminal pro-brain natriuretic peptide (NT-proBNP), Gensini score, Syntax score and proportion of Syntax≥23 were higher in T-wave upright group than in T-wave inversion group(all P＜0.05). Compared with the T-wave inversion group, the upright group had more cases of using vasopressor and longer average hospitalization day (all P＜0.05). Spearman correlation analysis showed that upright T wave in lead aVR was negatively correlated with LVEF, and positively correlated with Gensini and Syntax score, NT-proBNP, LVEF and hospitalization day (all P＜0.05). Multivariate Logistic regression analysis showed that upright T wave in lead aVR was independently associated with ejection fraction. Conclusions The patients of upright T wave in lead aVR with ACS three-vessel disease had lower LVEF values and worse clinical outcome than that of T wave inversion. Upright T wave in lead aVR can be used to evaluate the left ventricular function in patients with ACS three-vessel disease.