With the rapid development of modern science and technology and the in-depth research and exploration of medical researchers on coronary heart disease, the methods of diagnosing coronary heart disease have been improved day by day. In the early days, people mainly diagnosed myocardial infarction and coronary artery insufficiency based on typical clinical manifestations (including symptoms and signs), myocardial enzymatic examination and electrocardiographic features. In recent years, many new examination methods and techniques have been developed, such as radionuclide examination, echocardiography, coronary angiography, etc. used in the diagnosis of coronary heart disease. Clinical manifestations: mainly include symptoms and signs. Angina pectoris is the main symptom of coronary artery disease, and it is possible to distinguish angina pectoris from myocardial infarction according to the location, nature, trigger, duration, relief and other characteristics of angina pectoris attack and the accompanying symptoms and signs, and it can be said that the typical symptoms and signs are crucial to the diagnosis of coronary angina pectoris and myocardial infarction. Electrocardiogram: Electrocardiogram 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 easy to use, easy to popularize, and can be used to capture changes in a timely manner when the patient’s condition changes, and can be continuously and dynamically observed 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 is more clinically valuable, but of course, there are certain limitations. ECG load test: It mainly includes exercise load test and drug test (such as pansentine, isoproterenol test, etc.). ECG is the most commonly used 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 dilated coronary arteries, coronary blood flow can usually remain normal at rest without the manifestation of myocardial ischemia, and the 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 ECG is also essential for the evaluation of ischemic arrhythmias and cardiac function after myocardial infarction. Ambulatory ECG: It is a method that allows recording and editing of ECG changes in the heart during active and quiet states over a long period of time. This technique was first used by Holter in 1947 to monitor the electrical activity of the heart, so it is also known as Holter monitoring. The conventional ECG can only record the waveform of a resting state for a short period of only tens of seconds, while the ECG can continuously record up to 100,000 ECG signals within 24 hours, which can improve the detection rate of non-sustained ectopic rhythms, especially transient arrhythmias and transient episodes of myocardial ischemia. The time of presentation corresponds to the patient’s activity and symptoms.