Male sexual maturity is characterized by the development of adult male genitalia and the appearance of secondary male characteristics, such as enlarged testicles and scrotum, thickened penis, pubic hair, beard and armpit hair, thicker and lower voice, larger throat, taller body, and even erect penis and sperm discharge. Boys with the above characteristics before the age of 9 can be diagnosed as precocious puberty. Recently, an 8-year-old boy, Wang, was sent to the pediatric department of a local hospital by his parents for an erection in the early hours of the morning. The doctor told him that this is the adrenal glucocorticoid hormone, which has a structure similar to androgens, acting in the body of the child, and is not a sign of precocious puberty. It is reported that 30% of the children who went to the hospital for consultation on whether they were precocious were because of this condition mentioned above. The actual fact that one fifth of boys have an erection in the early hours of the morning is a normal physiological phenomenon, and parents need not be nervous. The adrenal glucocorticoid hormone in the body is released in pulses, reaching a peak in the early morning hours, and the structure of this hormone is similar to androgens, which will make the penis into an erection. In addition, when children see intimate images of both sexes on television and in pictures, the penis will become erect due to central stimulation, and this visual impact will promote a small amount of androgens, which may cause premature sexual maturity in children, and parents should be controlled to avoid as much as possible. There is also a possibility that a boy’s penis is enlarged due to congenital lack of 21 hydrogenase, which will contain too much androgen when the enzyme content is reduced, or adrenal sebaceous genital syndrome, and this phenomenon should be brought to the child for timely consultation. The most typical feature of precocious puberty in boys is testicular enlargement before the age of 9. Parents can identify whether precocious puberty has occurred in boys according to this phenomenon.