For children with premature onset of sexual characteristics, detailed medical history, comprehensive physical examination and relevant laboratory tests should be performed selectively to differentiate the types of precocious puberty and to determine the severity of the condition. In the process of treatment, regular follow-up and repeated physical examination should be conducted to examine the efficacy of treatment and further clarify and verify whether the original diagnosis is correct and the treatment plan is reasonable. a) Medical history questioning. Parents should be asked in detail about the time of the onset of secondary sexual characteristics and their progress; whether the child has any previous central nervous system disorders, the treatment at that time and the subsequent recovery; whether the child has taken any drugs or food containing sex hormones, the amount and duration of such drugs or food; the age of puberty of the parents, whether there are other patients with similar precocious puberty in the family and the onset of the disease, etc. b) Physical examination. Accurate measurement of height and weight and observation of physical development. Based on the development of external genitalia and secondary sexual characteristics, we will first determine whether it is homosexual or heterosexual precocious puberty, and make a judgment on the severity of the disease according to the development of secondary sexual characteristics. (c) Breast measurement. The measurement of the breast includes the measurement of the size of the appearance of the breast and the measurement of the size of the breast tissue. The development of breast tissue is directly influenced by hormones, especially estrogen, progesterone and prolactin, and its development can reflect the level of these hormones in the body, so the measurement of breast tissue size is valuable to determine the degree of sexual development. The size of the breast is influenced by the amount of glandular tissue, but also by the amount of fat in the breast. It is common to see children with simple obesity who have not yet developed puberty, but the appearance of their breasts can be larger, but they are mainly caused by the accumulation of fatty tissue, and there is no obvious breast tissue palpable in the breast. In addition, after effective treatment, the breast tissue can become significantly softer, reduce in size or even fade away and be replaced by fatty tissue in children with precocious puberty. However, there is often no significant change in the appearance of the breast size or only a slight reduction. Therefore, in judging the degree of sexual development, assessing the efficacy of treatment and differential diagnosis, all should be based on the measurement of the size of breast tissue. (d) Hypothalamic-pituitary-gonadal axis function measurement. Determination of serum gonadotropin levels LH, FSH, T, E2 and blood levels of 17α-OHP, a precursor substance of adrenocorticotropic hormone. If necessary, GnRH excitation test was performed. e) Ultrasound of the pelvis. Measure the size of the uterus and ovaries and observe the ovaries for developing follicles. If several follicles larger than 0.4 cm in diameter are present in the ovaries, this indicates the onset of pubertal development; if the follicles are larger than 1.5 cm in diameter, this indicates imminent ovulation. This can be used to determine the severity of the child’s condition. With effective treatment, the uterus and ovaries will shrink in size and the enlarged follicles will subside, so it can also be used to assess the efficacy and adjust the treatment plan. In addition, B-ultrasound can also be used to accurately determine the presence of occupying lesions such as ovarian cysts or solid tumors. f) X-ray bone age determination. Bone age refers to the age of skeletal development. Under normal circumstances, bone age is similar to biological age. In children with precocious puberty, the bone age is often significantly older than the biological age. In cases of simple breast development, the bone age is not advanced. In precocious puberty due to hypothyroidism, the bone age tends to be significantly behind the biological age. g) Cranial magnetic resonance imaging (MRI). The main exclusion is the presence of solid occupations in the saddle area. In children with central precocious puberty who are highly suspected of having intracranial occupying lesions at a younger age, even if no occupying lesions are currently detected, they should be followed up regularly with repeat examinations every 3-6 months.