A 12-year-old girl having menstruation for more than twenty days may be caused by the immaturity of the reproductive system, which can be treated by applying hemostatic drugs such as Baogong Hemostatic Granules, but the adverse effects are not yet clear. Because 12-year-old girls are relatively young, the ovarian function is underdeveloped, and the secretion of estrogen and progesterone may be unstable, resulting in menstruation for more than twenty days. If the bleeding is small and has no obvious effect on life, special treatment may not be needed and temporary observation is sufficient. If the bleeding is heavy, you can take some oral medicines to stop bleeding, such as Baogong Hemostatic Granules, which belongs to Chinese patent medicines and can be used for symptoms such as heavy menstruation and prolonged menstruation. It should be noted that the adverse reactions and contraindications of this drug are not clear. The 12-year-old girl appeared to menstruation more than twenty days, should be timely to the hospital, improve the relevant examination to clarify the cause of the disease, under the guidance of the doctor symptomatic treatment, avoid unauthorized use of drugs.