The coronary artery is a blood vessel supplying blood to the heart muscle. It has 2 branches, left and right, which open directly into the left and right aortic sinus at the root of the aorta, from which it begins to extend toward the surface of the heart and continuously branches into the heart, and because the blood and the vessel wall are equally impervious to light and overlap with the heart, atheromatous plaque or stenosis in the lumen of the vessel cannot be seen under ordinary X-ray. Selective coronary angiography is the use of specially shaped cardiac catheter percutaneously punctured into the femoral artery of the lower extremity along the descending aorta retrograde to the root of the ascending aorta, respectively, the catheter is placed at the mouth of the left and right coronary arteries, while the contrast agent is injected X-ray film camera, so that the entire left or right coronary artery trunk and its branches of the lumen can be clearly displayed, you can understand the presence of stenosis lesions, the location, extent, severity, and wall of the lesion. It can be used to make a clear diagnosis of the location, extent, severity, and condition of the vessel wall, to decide on a treatment plan (interventional, surgical, or medical), and to determine the efficacy of the treatment. This is a safe and reliable invasive diagnostic technique, which is increasingly accepted by the clinic and was once considered the “gold standard” for the diagnosis of coronary artery disease, with the advantages of integrating diagnosis and treatment. Coronary angiography is performed under local anesthesia, and there are no sensory nerves in the blood vessels or the heart, so the patient only feels slight pain during the puncture of the femoral or radial artery, but no significant discomfort during the rest of the procedure. Some patients may experience low back pain and discomfort, which may disappear after getting up and moving around. Complications can occur with any procedure, so the patient is asked to sign the form before the procedure. The complication rate of coronary angiography is 0.2% to 0.9%. In conclusion, coronary angiography is a very low risk, relatively safe and almost painless procedure. Nowadays, more than 90% of patients in the Department of Cardiology of the Union Hospital can undergo coronary angiography via the radial artery. Patients who undergo coronary intervention via the radial artery can have their arterial sheaths removed immediately after the procedure, and the radial artery can be compressed and fixed with pressure for 4-6 hours. Patients are free to move around immediately after the procedure. In recent years, since the clinical application of intracoronary ultrasound imaging (IVUS) and optical interferometric imaging (OCT), it has been found that intimal thickening or plaque can be detected in some of the vessels that appear normal in coronary angiography. Unless there is a high clinical suspicion of coronary artery disease (numerous risk factors, typical symptoms and abnormal changes in ECG) and the coronary angiogram is normal, the above tests should be considered.