Color Doppler ultrasound uses autocorrelation technology for Doppler signal processing, and the blood flow signals obtained by autocorrelation technology are computer color coded and then superimposed on a two-dimensional black-and-white image in real time, i.e., a color Doppler ultrasound blood flow image is formed. As a result, color Doppler ultrasound (i.e., color ultrasound) has the advantages of two-dimensional ultrasound structural images and provides rich information on hemodynamics at the same time, which has been popularized and used in clinical practice, and is known as “non-traumatic angiography” in clinical practice. The clinical use of the following aspects of the disease: (a) heart and vascular disease using 10MHz high-frequency probe can be found in the blood vessels less than 1mm plaque, carotid artery atherosclerosis occlusive disease has a better diagnostic value, but also the use of blood flow probing local amplification to determine the degree of narrowing of the lumen, embolism, whether there is a possibility of shedding, whether it produces ulcers, to prevent cerebral thrombosis occurs. Color ultrasound for all kinds of arteriovenous fistula can be said to be the best diagnostic method, when the probe to the colorful mosaic of ring color spectrum can be confirmed. For the heart morphology and structure, especially valve disease, congenital heart disease, detection of reflux beam and pressure, myocardial segmental movement abnormalities, cardiac function measurement, pericardial disease, cardiac connectivity large vessel disease, abdominal aortic aneurysm, vascular occlusive vasculitis, venous disease (including lower extremity varicose veins, the original occurrence of the deep venous valves of the lower limbs, the lower limbs of deep venous reflux obstruction, thrombophlebitis, and the formation of venous thrombosis and regression) using color ultrasound. The use of color ultrasound of high-definition, local magnification and blood flow spectroscopy can make a more correct diagnosis. (II) Abdominal organs It is mainly applied to liver and kidney, but it has certain auxiliary diagnostic value for the differentiation of benign and malignant lesions of tumors, the differentiation of gallbladder cancer and large polyps, chronic and severe inflammation, and the differentiation of choledochal ducts and hepatic arteries, etc. For liver cirrhosis, ultrasound can be used to diagnose from the liver to the liver. For cirrhosis, color ultrasound can make a better judgment from the size of the lumen of various blood vessels in the liver, the speed and direction of internal flow and the establishment of collateral circulation. For nodular sclerosis and diffuse hepatocellular carcinoma which are difficult to be distinguished by black and white ultrasound, it can be utilized to make differential diagnosis by high-frequency probing and blood flow spectrum probing. Color ultrasound used in the kidney is mainly used for renal vascular lesions, such as the aforementioned renal arteriovenous fistula, when the clinical manifestations of intervals, painless hematuria can not find the cause of the strong indications. For renal artery stenosis, one of the common causes of secondary hypertension, ultrasound can basically make a clear diagnosis, and when the blood flow velocity at the stenosis is greater than 150cm/s, the diagnostic accuracy reaches 98.6%, while the sensitivity is 100%. On the other hand, it is also the differential diagnosis of renal cancer, renal pelvis metastatic cancer and benign tumors. （Among the small organs, color ultrasound has obvious diagnostic accuracy compared with black-and-white ultrasound, mainly in thyroid, breast, eye, lymph nodes (including superficial lymph nodes, intra-abdominal mesenteric lymph nodes, retroperitoneal lymph nodes), and body surface masses. 10MHz probe without color flow Doppler is much clearer than the ordinary black-and-white ultrasound with 5MHz probe in a certain aspect. The diagnosis and differential diagnosis of thyroid pathology is mainly based on the blood supply of the thyroid gland, of which the image of hyperthyroidism is the most typical and specific, as a “sea of fire sign”. The presence or absence of nodules within the glandular echo and the surrounding blood flow can be well differentiated from nodular goiter, inflammatory changes of the thyroid (Hashimoto’s thyroiditis and subacute thyroiditis), thyroid adenomas, and thyroid cancer. If the diagnosis is not too clear and the patient has a certain degree of affordability, the patient can do a puncture test to further clarify the diagnosis. Breast ultrasound is mainly used for breast fibroma and breast cancer differential diagnosis, while the eye mainly has better diagnostic value for vascular lesions of the eye. (D) Prostate and seminal vesicles: Intracavernous transrectal exploration is the best method to diagnose prostate at present, so it is specially proposed here. In this method, the prostate gland is divided into zones (migratory zone, central zone, peripheral zone, and a part of the fibromuscular stroma of the prostate). The migratory zone is the origin of benign prostatic hyperplasia, and the peripheral zone includes the posterior part of the prostate and the apical part on both sides, which is the origin of 70-80% of cancers, while the apical part of the peritoneum is booked or even disappeared, forming an anatomically weak zone, which is the common metastatic channel of cancers, and is the key area of the biopsy of the prostate gland. Rectal examination has good diagnostic value for various prostate and seminal vesicle diseases, and when combined with prostate biopsy, the diagnosis is basically clear, and prostate diseases, especially prostate cancer, have been on the rise in our country, and the incidence of prostate cancer in Europe and the United States even ranked behind lung cancer, which is the second highest incidence of cancer, and abdominal examination of the prostate is basically unable to make a diagnosis, so it is recommended that the clinic use more rectal Therefore, it is recommended to use rectal ultrasound to diagnose prostate diseases without abdominal exploration if rectal exploration can be used. (E) Obstetrics and gynecology The main advantage of color ultrasound for obstetrics and gynecology is to identify benign and malignant tumors and umbilical cord disease, fetal heart disease and placental function assessment, for trophoblastic diseases have better diagnostic value, infertility, pelvic varicose veins through the observation of blood flow spectra, but also to make a diagnosis difficult to make under the black-and-white ultrasound. The use of vaginal probe has certain advantages over abdominal exploration, its superiority is mainly reflected in: ① uterine artery, ovarian blood sensitivity, high display rate. ①Sensitivity to uterine artery and ovarian blood flow, high display rate. ②Shorten the examination time and obtain accurate Doppler spectrum. ③No need to fill the bladder. ④It is not disturbed by obesity, abdominal scars, or bowel insufflation. ⑤ Judge the pelvis by looking for pelvic organ tenderness sites with the help of the activity of the probe tip.