Abstract: Objective The clinical features of gynecomastia in children and adolescents under 18 years old were analyzed retrospectively to explore the main influencing factors of gynecomastia in children and adolescents. Methods This study was a case-control study. The male patients with gynecomastia as the chief complaint and without drug intervention at the department pediatric endocrinology of the First Affiliated Hospital of Zhejiang University were enrolled into the gynecomastia group. The control group consisted of healthy boys of the same age. Height and weight were measured; body mass index (BMI) was calculated; sex hormone levels were detected by chemiluminescence immunoassay. Results The mean age of gynecomastia group (n=298) was (12.4±2.8). Gynecomastia reached its peak around the age of 11, and then showed a decreasing trend. G2 and G3 stage of sexual development accounted for 65.4%. The mean age of the control group (n=197) was (12.1±2.5). Logisitic regression analysis showed that BMI, T, FSH, LH, PRL and E2 / T were the risk factors of the gynecomastia. The sensitivity of the six indicators in combination was 0.748, and the area under the curve (AUC) was 0.813 (95% CI: 0.767-0.858). Conclusion The combination of BMI, T, E2/T, FSH, LH and PRL had a good predictive value for gynecomastia.