The reasons why menstrual blood keeps flowing are uterine fibroids, adenomyosis, abnormal uterine bleeding, placement of intrauterine device and so on. 1. Uterine fibroids: commonly found in large intermural fibroids and submucosal fibroids, which can increase the size of uterine cavity and endometrial area, and also cause dilatation and congestion of endometrial venous plexus, resulting in prolonged menstrual period and increased menstrual flow, etc. It can be clarified by combining with the history, ultrasonography and physical examination. 2. Adenomyosis: It can also increase the endometrial area and myometrial fiber proliferation, which can cause prolonged menstrual period, excessive menstrual flow, and progressive aggravation of dysmenorrhea. The combination of history and ultrasonography and physical signs can assist in the diagnosis. 3. Abnormal uterine bleeding: such as irregular endometrial shedding, endometrial polyps, etc., can also cause prolonged menstruation, which can be diagnosed by history, ultrasonography and hysteroscopy. 4. Placement of intrauterine device: due to the stimulation of the endometrium by the device, it can also cause prolonged menstruation, increased menstrual flow and other side effects, which can be gradually recovered in 3-6 months, and the combination of medical history and ultrasound examination can assist in the diagnosis. When the menstrual blood does not stop flowing, it is necessary to go to the hospital in time in order to identify the cause as soon as possible and actively deal with it under the guidance of the doctor.