Yin ultrasound is a kind of intracavernous ultrasound, which is a method of ultrasound examination by placing the ultrasound probe directly in the vagina, and the probe is close to the cervix and the posterior fornix in the vagina unlike abdominal ultrasound, the sound beam has to pass through the abdominal skin and muscles, so the pelvis is displayed more clearly. Especially for the observation of posterior uterus, endometrial cancer, uterine fibroids, placenta praevia, etc., the image display is significantly clearer than the abdominal ultrasound, and the detection of early and early pregnancy is found about 5 days earlier than the abdominal ultrasound, and the patient doesn’t need to hold his urine during the examination. Obese patients can also have a clearer image of the vaginal ultrasound, so obese patients are more suitable for vaginal ultrasound examination.