Brownish colored uterine fluid can occur in an acidic vaginal environment or in the case of old bleeding. When uterine fluid occurs, there is a small amount of bleeding from the vagina and cervix, and a brown or coffee-colored discharge may form as a result of the acidic environment of the vagina. If left untreated for a prolonged period of time, it not only tends to lead to brown discharge, but may also cause inflammation. If there is stale bleeding it can also make the discharge brown in color. Uterine fluid is mostly seen after abortion, medication abortion for scraping, diagnostic scraping or hysteroscopic removal of polyps, hysteroscopic removal of the ring, hysteroscopic removal of submucosal leiomyomas and other surgeries, resulting in damage to the mucous membrane of the uterine cervix, and the fluid is not easy to be discharged. With the gradual prolongation of the time of blood flow out of the blood vessels, the color of the blood will gradually deepen, which can be manifested as brown, dark brown, and may even turn into black secretion. Once the situation of uterine fluid occurs, it is necessary to judge whether treatment is needed according to the patient’s situation, but if there are uncomfortable symptoms, it is recommended to seek medical treatment as soon as possible.