Ultrasound was first applied to diagnose heart disease in 1954. Echocardiography is a preferred noninvasive technique that uses the special physical properties of ultrasound to examine the anatomical structure and functional status of the heart and great vessels. Three types are commonly used clinically: M-mode, 2D and Doppler echocardiography. Those that are being investigated and have begun initial clinical use include real-time 3D echocardiography, various types of stress echocardiography (including exercise and drug-induced), transesophageal echocardiography, acoustic imaging, and tissue Doppler. I. Common patient position and breathing: In general, the left lateral and horizontal positions are taken, and the right lateral position is taken by the right heart. Patients generally calm breathing on, a few more lung gas can breathe at the end of breath hold. Second, the probe selection: can choose adult and pediatric probe, according to the purpose of the examination can choose conventional cardiac ultrasound probe, transesophageal ultrasound, load ultrasound, etc. Third, the sound window: conventional ultrasound has four sound windows: parasternal, apical and subxiphoid, and superior sternal recess; special cases of right-positioned heart at the right edge of the sternum, transesophageal. Examination modes and methods: On the basis of two-dimensional mode, M mode, color multispectral mode, spectral multispectral, tissue multispectral, etc. are selected according to the need, and generally multiple modes are used in combination to obtain information in many aspects and to conduct comprehensive analysis. V. Clinical applications: Real-time observation of the heart and macrovascular structure has important diagnostic value for pericardial disease, congenital heart disease, various heart valve diseases, complications of acute myocardial infarction (such as septal perforation, papillary muscle rupture, ventricular wall tumor, pseudoventricular wall tumor), and intra-cardiac appendage thrombus. It is also useful for the diagnosis of cardiac masses, coronary artery disease, pericardial disorders, hypertensive heart disease, pulmonary heart disease, prosthetic valve follow-up, and large vessel disorders. It also allows dynamic observation of ventricular wall motion to detect segmental motion abnormalities caused by myocardial ischemia. It can measure blood flow velocity and pressure, including antegrade and regurgitant flow, to analyze valve stenosis and obstructive disease and right heart pressure measurement; systolic and diastolic function can be measured using the software. Three-dimensional reconstruction mainly wants to solve the quantitative analysis of the heart and provide a clearer three-dimensional structure, various load echocardiograms mainly to improve the diagnostic value of echocardiography for coronary artery disease, and cardiac angiography to assess local myocardial perfusion, which are currently in the scientific experimental research stage. Transesophageal echocardiography is a supplement to transthoracic echocardiography, which has been carried out in a few large hospitals in China. The main applications are: determining the source of emboli, especially for transthoracic echocardiography that cannot obtain satisfactory images and left auricular thrombus, infective endocarditis, aortic coarctation, and intraoperative monitoring. Intravascular ultrasound is mainly used in the coronary arteries, using a catheter with a diameter of 1.1 to 1.8 mm with an ultrasound probe at the tip, which can be placed at the site of the coronary lesion to better observe the lesion shape and determine the lesion composition based on the echo characteristics, which is superior to coronary angiography. It can also be used to observe structural changes in the coronary arteries after percutaneous transluminal coronary angioplasty (PTCA).