9 years old girl breast bulge is normal, the level of normal sexual development of girls is, if 8 weeks old before the long breast is called precocious puberty. Premature sexual development of girls will affect the adult lifelong height, will lead to adult lifelong height is too short, need to take the child to the hospital to carry out the following checks: 9-year-old girl chest bulge is regarded as normal, but it is best to go to the hospital to do a health checkup.1, the detection of bone age, that is, the orthopedic film of the left wrist joints, to make clear that the child’s actual height and the height of the age of the bone is the same or not, if it belongs to the shortness of the child then need to be further examined.2, the need to Examination of the uterus, ovaries and breast ultrasound to clarify the current level of sexual development of the child. If the degree of sexual development of the child is more serious according to the comprehensive bone age examination, it is necessary to apply medication to control it, and if the child’s height is short, it is necessary to apply growth hormone to treat the growth of the child.