With the continuous development of ultrasound diagnostic instruments and diagnostic technology, from the earliest A-shaped ultrasound, B-shaped ultrasound, M-shaped ultrasound to the current Doppler ultrasound, color flow imaging technology, intracavitary ultrasound, interventional ultrasound, three-dimensional ultrasound stereoscopic imaging, as well as the improvement of ultrasound grayscale and the strengthening of real-time imaging technology, thus making ultrasound examination provide more and more accurate diagnostic information for the clinic. Transabdominal ultrasound is becoming the most common examination method and means of obstetrical and gynecological ultrasound, while transvaginal ultrasound provides a good examination pathway for obstetrical and gynecological ultrasound technology, so that posterior pelvic masses, intrauterine cavity diseases, early pregnancy, follicle detection, etc. can be more clearly diagnosed than transabdominal ultrasound, improving It has improved the diagnostic compliance rate of ultrasound. Transvaginal ultrasound is a type of intracavitary ultrasound that uses a special vaginal probe placed directly in the vagina to perform ultrasound examinations. Transvaginal ultrasound is characterized by high frequency and high resolution, and the patient does not need a full bladder. Transvaginal ultrasound observes embryonic development and structures 5-7 days earlier than transabdominal ultrasound, such as early intrauterine pregnancy, follicle detection, early microscopic fibroids, ectopic pregnancy, uterine malformations, and postmenopausal endometrial thickness, which can be observed and measured more clearly and accurately than abdominal ultrasound. Transvaginal ultrasonography has become one of the important means of obstetrical and gynecological ultrasonography since it has entered clinical application. The advantages of transvaginal ultrasound: 1, transvaginal ultrasound is used more frequently, the probe is close to the cervix and posterior fornix in the vagina, and the observation images of posterior uterus, intrauterine lesions, posterior pelvic masses, ovarian follicle detection located in the posterior pelvic cavity, early displaced pregnancy, early pregnancy, etc. are displayed more clearly than transabdominal ultrasound. 2.Patients do not need to fill the bladder, and the pelvic organs are in a natural state. 3.For obese patients, when making vaginal ultrasound examination, because the probe is close to the vault and close to the target organs, the ultrasound decay is reduced and the resolution is high. 4. Transvaginal ultrasound-guided puncture is currently the most common route for interventional ultrasound. Limitations of transvaginal ultrasound 1.The focus area of transvaginal probe is within 10cm. For example, if the uterus exceeds the pelvis after 13 weeks of gestation, middle and late pregnancy, large pelvic masses and uterine fibroids, transvaginal ultrasound cannot show the whole picture and transabdominal ultrasound is needed. 2. Because the vaginal probe needs to be placed inside the vagina for operation, it is not suitable for unmarried women, menstruating women, those with vaginal deformities and obvious vaginal atrophy after menopause, and those with vaginal inflammation.