Echo mass with blood flow signal in the uterine cavity is considered to be pregnancy, endometrial polyp, uterine fibroid, endometrial cancer, etc. Whether it is serious or not is related to the specific situation. 1. Pregnancy: after pregnancy, blood circulation will be established between the uterus and ovaries, and ultrasound examination will show that there are blood flow signals in the echogenic mass in the uterine cavity, which is a normal phenomenon. 2. Endometrial polyps: endometrial polyps are overgrowth of local mesenchyme of the uterus covered with benign glandular epithelium, which is composed of endometrial glands, mesenchyme and blood vessels, and this is a common disease, most of which are not serious. 3. Uterine fibroids: uterine fibroids are formed by the proliferation of uterine smooth muscle tissue, also a common disease, most of them are benign, not particularly serious. However, if the nuclear division is active, it may have malignant potential, which is relatively serious, and timely surgery is necessary. 4. Endometrial cancer: endometrial cancer is a kind of epithelial malignant tumor, which will also show abnormal echogenicity in the uterine cavity and blood flow signals, which is a more serious disease and may threaten the patient’s life. There may be other reasons for the echogenic mass with blood flow signal in the uterine cavity, whether it is serious or not should be analyzed under the guidance of doctor, if it is more serious, it should be treated actively.