Ovarian fluid dark area is considered to be related to ovarian physiologic cysts and ovarian pathologic cysts. 1. Ovarian physiologic cysts: due to the cyclic changes of follicles in the ovary, so the patient will have follicular cysts, corpus luteum cysts and other physiologic cysts, usually after the menstrual period is cleared the cysts can disappear on their own. 2. Pathologic cysts of the ovary: (1) Ovarian chocolate cyst: due to the ectopic endothelium planted on the ovary, with the change of menstrual cycle, the menstrual blood gradually retention and the formation of cysts, ultrasound shows mud-like echoes. (2) Mature teratoma: the cause of its development is still unclear, the patient will have lower abdominal distension, pain and other discomforts, ultrasound shows that the localization is accompanied by strong echoes of dots or stars. For patients who are found to have ovarian fluid dark area, it is recommended that they go to the gynecology department of regular hospitals to improve the ultrasound, tumor markers and other related examinations, and then actively treat under the guidance of the doctor after the cause of the disease is clearly defined.