Gynecomastia，the most common benign disease of the breast in men，is a primary disease in most case，mainly due to the imbalance of endogenous estrogen and androgen，resulting in hyperplasia of glands and hypertrophy of adipose tissue. The clinical feature of the disease is the enlargement of the bilateral or unilateral breast tissue. Simon’s classification is the most commonly used grading method，and the main treatment methods are drug treatment and surgical treatment. This is a review about the cause，type and treatment of gynecomastia，especially the advantages and disadvantages of the common treatment methods.