Objective To investigate the correlation between glycosylated hemoglobin A1c (HbA1c) and severity of coronary artery lesions in young men with acute myocardial infarction (AMI). Methods Total 278 young men with AMI less than 45 years old were retrospectively studied, and all of them were admitted to hospital from January 2009 to December 2011, and had undergone coronary angiography. According to the results of coronary angiography, the patients were divided into three groups based on the number of artery lesions: the single group (156 cases), the double group (64 cases) and the triple group (58 cases). The relationship between the severity of coronary artery lesions and the following factors were observed: HbA1c, systolic blood pressure (SBP), diastolic blood pressure (DBP), hemoglobin (Hb), serum uric acid (UA), total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), body mass index (BMI), smoking history, drinking history and family history of early coronary artery disease. Results a) HbA1c levels were gradually raised in all the three groups, but the single group (6.39±1.67%) was significantly lower than the double group (6.91±1.63%) and the triple group (7.41±2.12%), with significant differences (Plt;0.05); the HbA1c level of the single group was significantly lower than the triple group in both the ST-segment elevation AMI (6.42±1.68% vs. 7.17±1.86%, Plt;0.05) and the non-ST-segment AMI (5.57±0.37% vs. 8.56±2.83%, Plt;0.05); the HbA1c level of the single group was significantly lower than the triple group in patients with diabetes millitus (8.31±1.83% vs. 8.59±2.02%, Plt;0.05) and in patients without diabetes millitus (5.56±0.33% vs. 5.74±0.37%, Plt;0.05); b) There were significant differences in SBP, TC, HDL-C, LDL-C and drinking history between the single group and the other two groups (all Plt;0.05), and there were significant differences in DBP and TG between the single group and the double group (all Plt;0.05); and c) The results of logistic regression analysis showed that, LDL-C (OR=1.790), HbA1c (OR=1.287) and SBP (OR=1.042) were the independent risk factors (all Plt;0.05) for multiple lesions in coronary arteries of young men with AMI. Conclusion Glycosylated hemoglobin A1c is an independent risk factor for multiple lesions in coronary arteries of young men with AMI.