The black discharge from the vagina is the blood component. If the vaginal bleeding is small and stays in the uterine cavity for a long time, it gradually becomes obsolete bleeding and usually manifests as black discharge. There are several common reasons for this situation: 1. gynecological inflammation: some chronic inflammatory diseases usually also have a small amount of bleeding, and sometimes it also manifests as black discharge; 2. hormonal instability: at this time, along with hormonal withdrawal there will be A small amount of bleeding, such as luteal insufficiency, luteal atrophy incomplete, there will be a small amount of bleeding before and after menstruation, a small amount of bleeding will also be manifested as black discharge; 3, gynecological tumors: especially early lesions or benign lesions, such as endometrial polyps will lead to a small amount of bleeding, this bleeding in the uterine cavity, vaginal stay longer, it will be manifested as black discharge. In the above cases, it is recommended to visit a hospital and identify the cause, and deal with it as appropriate according to the cause.