During ovulation, there is black blood in the vagina, the main consideration is ovulation bleeding. More bleeding during ovulation is caused by a transient decrease in estrogen level. Before ovulation, estrogen level is relatively high, and after ovulation, hormone level rapidly decreases, resulting in endometrial exfoliation and bleeding. However, after ovulation, the corpus luteum secretes estrogen and progesterone again, so female hormones rise again and the bleeding gradually decreases and stops. Ovulation bleeding that occurs once in a while does not require special examination or treatment. If it occurs three or more times consecutively, relevant tests are needed to rule out bleeding caused by organic pathologies, such as cervical cancer, endometrial polyps, ovarian cancer, etc. Screening is needed through TCT of the cervix, HPV screening, gynecological ultrasound, hysteroscopy if necessary, diagnostic curettage, and female tumor markers.