1, cervical canal stenosis is mainly due to the obstruction of menstrual flow, causing dysmenorrhea. 2.Uterine dysplasia Poor uterine development is easily combined with abnormal blood supply, resulting in uterine ischemia, hypoxia and causing dysmenorrhea. 3.Uterine position abnormality If the position of the uterus is extremely retroflexed or anteriorly flexed, it can affect the smooth flow of menstrual blood and cause dysmenorrhea. 4, mental, neurological factors, some women are over-sensitive to pain. 5, genetic factors, the daughter of dysmenorrhea and mother dysmenorrhea has a certain relationship. 6, endocrine factors menstrual abdominal pain and luteal phase progesterone elevation. 7, the endometrium as well as menstrual blood prostaglandin (PG) content is elevated, prostaglandin E2 (PGE2) has a role in the uterine muscle fibers so that the contraction of dysmenorrhea caused by patients with the endometrial tissue of the endometrium of the prostaglandin content of normal women significantly higher. 8, excessive contraction of the uterus, although dysmenorrhea patients uterine contraction pressure and normal women basically the same (normal pressure of about 4.9Kpa), but the uterine contraction lasts longer, and often not easy to completely relax, so the occurrence of uterine contraction due to excessive dysmenorrhea. 9, abnormal uterine contraction, dysmenorrhea patients often have abnormal uterine contraction, which often leads to uterine smooth muscle ischemia, uterine muscle ischemia can cause spasmodic uterine muscle contraction, resulting in pain and dysmenorrhea. 10, gynecological diseases such as endometriosis, pelvic inflammatory disease, adenomyosis, uterine fibroids, etc., uterine placement of birth control devices (commonly known as the birth control ring) is also easy to cause dysmenorrhea. 11, the first period of young girls, psychological pressure, sedentary, resulting in poor circulation of blood, menstrual blood run poorly, love to eat cold food and other causes of dysmenorrhea. 12, menstrual period of strenuous exercise, by the wind, cold, wet and cold invasion, are easy to trigger dysmenorrhea. 13, the air is not good by some industrial or chemical nature of the odor stimulation, such as gasoline, caramel water, etc. caused by dysmenorrhea.