Due to individual differences, women’s menstrual period is generally 2~8 days, menstrual period of 40 days is a serious abnormal phenomenon, mostly due to anovulatory dysfunctional uterine bleeding, endometritis, uterine fibroids, thrombocytopenic purpura and other factors. 1. Anovulatory dysfunctional uterine bleeding: it can be due to the feedback regulation between hormones of HPO axis has not matured, unable to form luteinizing hormone to promote ovulation, or due to stress, polycystic ovary syndrome, etc., resulting in the endometrium stimulated by a single estrogen without progesterone to counteract the causes, leading to the phenomenon of women’s menstruation for more than 40 days. 2. Endometritis: it is caused by pathogenic microorganisms infecting the endometrium, and patients usually have lower abdominal pain, fever, increased vaginal discharge and prolonged menstrual period, leading to the phenomenon of women having menstrual periods of more than 40 days. 3. Uterine fibroids: uterine fibroids can also lead to the phenomenon of 40 days of menstruation, long-term blood loss, but also cause anemia, and will be accompanied by an increase in vaginal discharge, urinary frequency, urinary urgency, lower abdominal discomfort and other phenomena, and may even affect the pregnancy. 4. Thrombocytopenic purpura: patients can be due to thrombocytopenia, so that the blood clotting function decreased, resulting in skin, mucous membrane petechiae, purpura, and will be accompanied by fatigue, hematuria, fever and other symptoms, and female patients will also have prolonged menstrual period, such as menstruation for more than 40 days. In addition, there are many other causes can cause menstrual period more than 40 days, we recommend that patients go to the hospital in a timely manner to find out the cause of the disease, and then follow the doctor’s instructions for treatment.