(1) ECG: ECG is the earliest, most commonly used and most basic diagnostic method in the diagnosis of coronary heart disease. Compared with other diagnostic methods, ECG is convenient to use and easy to popularize. 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 it is 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 also certain limitations. (2) ECG load test: It mainly includes exercise load test and drug test (such as pansentine, isoproterenol test, etc.). ECG is the most common and simple method for clinical observation of myocardial ischemia. When angina attacks, ECG can record the abnormal ECG manifestations of myocardial ischemia. However, in many patients with coronary artery disease, despite the fact that the maximum reserve capacity of coronary artery dilation has decreased, coronary blood flow can usually remain normal at rest without myocardial ischemic manifestations, and the ECG can be completely normal. To reveal reduced or relatively constant blood flow, the presence of angina can be confirmed by loading the heart with exercise or other methods that induce myocardial ischemia. Exercise testing is also essential for the evaluation of cardiac function after ischemic arrhythmias and myocardial infarction. (3) Ambulatory ECG: It is a method that allows continuous recording and compilation and analysis of ECG changes in the heart during 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 called Holter monitoring. The conventional ECG can only record waveforms of a few tens of cardiac cycles at rest, but the ECG can record up to 100,000 ECG signals continuously in 24 hours, which increases the detection rate of non-sustained ectopic rhythms, especially transient arrhythmias and transient episodes of myocardial ischemia, thus expanding the clinical use of the ECG, and the time of appearance can correspond to the patient’s activity and symptoms. The time of presentation can correspond to the patient’s activity and symptoms. (4) Nuclear myocardial imaging: Based on the medical history, this test can be performed 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. The detection rate can be improved by combining with exercise test and re-imaging. (5) Coronary angiography: It is the current “gold standard” for the diagnosis of coronary artery disease. It can clarify the presence or absence of coronary artery stenosis, the location, degree and extent of stenosis, and can guide the measures to be taken for further treatment accordingly. 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. (6) Ultrasound and intravascular ultrasound: Cardiac ultrasound can examine the morphology of the heart, ventricular wall motion and left ventricular function, and is one of the most commonly used examination methods. It has important diagnostic value for ventricular wall tumor, intra-cardiac thrombus, heart rupture, and papillary muscle function. Intravascular ultrasound can clarify the wall morphology and degree of stenosis within the coronary arteries, which is a promising new technology. (7) Myocardial enzymatic examination: It is one of the important tools for the diagnosis and differential diagnosis of acute myocardial infarction. The clinical diagnosis of acute myocardial infarction can be clearly made on the basis of definite enzymatic changes such as serial changes in serum enzyme concentration and elevation of specific isoenzymes. (8) Cardiac blood pool imaging: It can be used to observe the dynamic images of ventricular wall systole and diastole, which is an important reference value for determining ventricular wall motion and cardiac function.