Menstruation refers to menstruation, and a girl’s menstruation at the age of nine and a half is generally abnormal, and may be due to precocious puberty. Girls usually enter puberty when they are 9-11 years old, and secondary sexual characteristics begin to appear gradually. Breast development is usually the earliest of the secondary sexual characteristics to appear before the age of 8, which is considered precocious puberty, and from breast enlargement to the first menstruation will usually take 2.5~3 years. If a girl has her period at the age of 9.5 years, she may have started to develop her secondary sexual characteristics at the age of 6-7 years, which is considered precocious puberty and is not normal. If a girl is 9.5 years old and has menarche, she can go to the hospital in time to see a doctor and get a clear picture of her condition, and then under the guidance of the doctor to carry out the relevant treatment.