If a boy is 12 years old and already has sexual developmental characteristics, such as the appearance of throat knots, voice change, armpit hair, pubic hair and other appearances, as well as penis enlargement, this situation is normal sexual developmental characteristics. The criteria for judging the precociousness of children, girls are less than 8 years old to appear sexual development characteristics; boys appear sexual development characteristics before the age of 9 years old, this age range belongs to the category of precociousness. The child is generally 12 years old and has reached the age of sexual development, the characteristics of sexual development is a normal process, parents do not need to worry too much. However, if the child is behind or significantly ahead of schedule, bone age and sex hormone levels can be tested. If the bone age is significantly early and the sex hormone level is significantly over the limit, the child can be given timely intervention to prevent the final height from being short.