A small amount of brown blood flowing from the vagina for more than 20 days is abnormal uterine bleeding with many causes, such as pre-eclampsia, endometritis, endometrial hyperplasia, and uterine fibroids. The patient needs to seek medical attention in a timely manner to identify the specific cause, and to carry out cause-specific treatment as well as hemostatic treatment to avoid the progression of the original disease and the occurrence of anemia.1. Pre-eclampsia: If the patient is pregnant, factors such as fetal chromosomal abnormalities, chemical stimulation and viral infection can trigger pre-eclampsia, resulting in symptoms such as small amount of brown blood flowing from the vagina for more than 20 days, which may be accompanied by abdominal pain. It is recommended to consult a doctor in time and take drugs such as detrofloxacin and progesterone as prescribed by the doctor for fetal preservation treatment. Clinically, it can be treated with antibiotics such as ceftriaxone sodium and cefoxitin sodium. However, patients with large amount of pus in the uterine cavity need to be treated with uterine drainage. 3. Endometrial hyperplasia: Women with early menarche or late menopause are prone to endometrial hyperplasia, which is mainly manifested by irregular vaginal bleeding that lasts for a long time up to about 20 days. To avoid dizziness, weakness and even shock due to excessive bleeding, it is recommended to seek medical treatment in a timely manner. Under the guidance of a doctor, treatment with estrogenic drugs such as medroxyprogesterone acetate and detroxyprogesterone and, if necessary, surgery is required. 4. Uterine fibroids: factors such as abortion, gynecological inflammation and hormonal imbalance may induce uterine fibroids. The disease is often accompanied by increased menstrual flow and prolonged menstrual periods, which can lead to a small amount of brown blood flowing from the vagina for more than 20 days. Since the associated pathological manifestations are already present, treatment should be done with hemostatic drugs such as tranexamic acid, as well as iron and misoprostol, as prescribed by the doctor. In addition, patients who meet the indications for surgery can also undergo surgical excision; 5. Cervical cancer: early stage cervical cancer patients may not have obvious symptoms, and some of them may show a small amount of bleeding after sexual intercourse. If it is clear that the patient has cervical cancer, she needs to undergo surgery, supplemented by radiotherapy, etc.; 6. Other: If a woman has an intrauterine device, this bleeding may be caused by abnormal uterine bleeding due to the inhibition of uterine contraction by the device. Most of the patients can basically disappear on their own after their bodies adapt to the IUD, but if there is no improvement for a long time, they can visit the hospital in time and remove the IUD if necessary.