Dark-colored discharge on the 20th day of hysteroscopic surgery may be caused by endometrial damage, cervical erosion, vaginal inflammation and other reasons. 1. endometrial damage: hysteroscopic surgery has some damage to the endometrium, postoperative wound healing is poor, there will be some blood from the wound penetration, through the vagina out of the body, 20 days after hysteroscopy normal surgery caused by the wounds have been fully recovered, can not be ruled out is the onset of menstruation, you can come to the hospital to be evaluated by a specialist physician. 2. Cervical erosion: If the patient has cervical erosion, after hysteroscopic surgery, the patient may be stimulated by the surgery, resulting in a small amount of blood oozing out of the blood vessels on the surface of the cervical erosion, forming a dark-colored secretion. Cervical cytology and cervical human papillomavirus examination are needed. If cervical lesions are found, standardized treatment is required as prescribed by the doctor. 3. Vaginal inflammation: If there is a combination of bacterial vaginitis, mycosis vaginalis or trichomonas vaginitis and other infections. Prolonged inflammatory stimulation will produce a large number of inflammatory factors, leading to increased permeability of the blood vessels on the surface of the vagina and cervix, and destruction of the local blood vessels of the cervix and vagina, which will lead to extravasation of the blood, resulting in the formation of dark-colored secretions. In addition to the above, there may be other reasons for the dark-colored discharge 20 days after hysteroscopic surgery. It is recommended to seek prompt medical attention to identify the cause and treat it aggressively if necessary.