(1) Electrocardiogram: Electrocardiogram is the earliest, most commonly used and most basic diagnostic method in the diagnosis of coronary artery disease, and compared with other diagnostic methods, electrocardiogram is convenient and easy to use. When the patient’s condition changes, the changes can be captured in time and continuous dynamic observation and various load tests can be performed to improve its diagnostic sensitivity. Whether angina pectoris or myocardial infarction, there are typical ECG changes, especially for the diagnosis of arrhythmia has its clinical value, but of course, there are certain limitations. (2) ECG load test: mainly including exercise load test and drug test (such as pansentine, isoproterenol test, etc.), ECG is the most common simple method for clinical observation of myocardial ischemia. When angina attacks, ECG can record abnormal ECG manifestations of myocardial ischemia, but in many patients with coronary artery disease, despite the fact that the maximum reserve capacity of coronary artery dilation has been reduced, usually the coronary blood flow can still be maintained at rest without myocardial ischemic manifestations, and ECG can be completely normal. To reveal reduced or relatively fixed blood flow, the presence of angina can be confirmed by exercising or other methods that load the heart and induce myocardial ischemia. Exercise testing is also essential for the evaluation of cardiac function after ischemic arrhythmias and myocardial infarction. (3) Ambulatory electrocardiography: It is a method that can continuously record and compile and analyze electrocardiographic changes of the heart in active and quiet states for a long period of time. This technique was first used by Holter in 1947 to monitor electrical activity, so it is also known as Holter monitoring. Conventional ECG can only record waveforms of only a few dozen heart cycles at rest, while ambulatory ECG can continuously record up to 100,000 ECG signals within 24 hours, which can improve the detection of non-sustained ectopic rhythms, transient arrhythmias and transient The detection rate of non-sustained ectopic rhythm, transient arrhythmias and transient myocardial ischemic attacks can be improved, thus expanding the scope of clinical use of ECG, and the time of appearance can correspond to the patient’s activity and symptoms. (4) Multi-layer spiral CT: From 2-layer to the current 256-layer spiral CT, the scanning speed is faster, the temporal and spatial resolution is greatly improved, and it is less affected by breathing and heart rate, which provides a safe and reliable means for non-invasive examination of coronary heart disease. Its diagnostic sensitivity for patients with coronary artery disease is over 80% and specificity is over 90%. Using multilayer spiral CT, it is possible to evaluate the degree of coronary artery stenosis, analysis of the degree of calcification, variation, and the effect of hemodynamic reconstruction. (5) Nuclear myocardial imaging: According to the medical history, this test can be done when angina cannot be ruled out by ECG examination. Nuclear myocardial imaging can show the ischemic area and clarify the site and extent of ischemia, and the detection rate can be improved by combining with exercise test and re-imaging. (6) Coronary angiography: It is the “gold standard” for the diagnosis of coronary artery disease, which can clarify the presence or absence of stenosis in the coronary arteries, the degree and extent of stenosis, and can guide the measures to be taken for further treatment. At the same time, left ventriculography can be performed to evaluate cardiac function. The main indications for coronary angiography are: ① For those who have severe angina despite medical treatment, to clarify the arterial lesion in order to consider bypass graft surgery; ② For those whose chest pain resembles angina but cannot be diagnosed. (7) Ultrasound and intravascular ultrasound: Cardiac ultrasound can examine heart morphology, ventricular wall motion and left ventricular function, and is one of the most commonly used examinations, which has important diagnostic value for ventricular wall tumors, intra-cardiac thrombus, heart rupture and papillary muscle function. Intravascular ultrasound can clarify the wall morphology and degree of stenosis within the coronary arteries, and is a promising new technology. (8) Myocardial enzymatic examination: It is one of the important tools for the diagnosis and differential diagnosis of acute myocardial infarction. Clinically, the diagnosis of acute myocardial infarction can be clearly made based on the sequence changes of serum enzyme concentration and specific isoenzyme elevation and other affirmative enzymatic changes. (9) Cardiac blood pool imaging: It can be used to observe the dynamic images of ventricular wall systole and diastole, which has important reference value for determining ventricular wall motion and cardiac function.