Uneven thickening of endometrium is usually related to endometritis, endometrial polyps, endometrial cancer and other causes. 1. Endometritis: endometritis refers to the inflammation that occurs when bacteria break through the defense of the cervix and invade the endometrium, which is one of the pelvic inflammatory diseases. Repeated episodes of endometritis will lead to congestion and edema of the endometrium, which will show thickening of the endometrium. 2. Endometrial polyp: endometrial polyp is a common uterine cavity lesion in which the uterus localized endometrial overgrowth. It can be a single lesion or multiple lesions, with diameters varying in size from several millimeters to several centimeters. Patients with small endometrial polyps may show uneven thickening of the endometrium on ultrasound. 3. Endometrial cancer: endometrial cancer is a group of epithelial malignant tumors occurring in the endometrium, which is one of the three major malignant tumors in female reproductive tract. When suffering from endometrial cancer, the phenomenon of uneven thickening of endometrium will easily appear on color ultrasound. When uneven thickening of endometrium appears in color ultrasound, one should consult a doctor in time and get a clear diagnosis and treatment under the doctor’s guidance.