Electrocardiogram (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 easy to use and popularize. When the patient’s condition changes, it can capture the changes in a timely manner, and can be continuously observed dynamically and carry out various load tests 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 some limitations. Second, the ECG load test mainly includes exercise load test and drug test (such as Pansentin isopropyl renal test, etc.). Electrocardiogram is the most commonly used and simple method for clinical observation of myocardial ischemia. When angina attack occurs, ECG can record the abnormal ECG manifestations of myocardial ischemia. However, in many patients with coronary artery disease, although the maximal reserve capacity for coronary artery dilatation has decreased, coronary blood flow can usually be maintained at rest without myocardial ischemia and the ECG can be completely normal. In order to reveal reduced or relatively constant blood flow, myocardial ischemia can be induced by loading the heart through exercise or by other means, thus confirming the presence of angina pectoris. Exercise test is also essential for the evaluation of cardiac function after ischemic arrhythmia and myocardial infarction. Ambulatory electrocardiography (ECG) is a method of continuously recording and compiling and analyzing the changes in the ECG of the heart in both active and quiet states over 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 electrocardiograms can only record waveforms of only a few dozen cycles in the resting state, whereas ambulatory electrocardiograms can record up to 100,000 ECG signals continuously over a 24-hour period. This improves the detection of non-sustained ectopic rhythms, especially transient arrhythmias and transient ischemic episodes. Thus, the scope of clinical use of ECG is expanded, and the time of appearance can correspond to the patient’s activities and symptoms. Nuclide myocardial imaging can be done when angina pectoris cannot be excluded by ECG according to the medical history. Nuclide myocardial imaging can show the ischemic area to clarify the location and range of ischemia, and the detection rate can be improved by combining with exercise test and reimaging. Coronary angiography is the “gold standard” for the diagnosis of coronary heart disease, which can clarify whether the coronary artery is stenotic or not, and the location, degree and scope of stenosis. Accordingly, it can guide the measures to be taken for further treatment. At the same time, left ventriculography can be performed to evaluate heart function. The main indications for coronary angiography are: 1, to the internal medicine treatment of angina is still more serious, clear arterial lesions in order to consider bypass grafting surgery; 2, chest pain like angina and can not be diagnosed. Sixth, ultrasound and intravascular ultrasound cardiac ultrasound can be cardiac morphology wall motion and left ventricular function examination, is currently one of the most commonly used means of examination. It has important diagnostic value for ventricular wall tumor, intracavitary thrombus, cardiac rupture and papillary muscle function. Intravascular ultrasound can clarify the morphology of the wall and the degree of stenosis in the coronary arteries is a promising new technology. Seven, myocardial enzyme examination is an important means of diagnosis and differential diagnosis of acute myocardial infarction. Clinically, according to the sequence change of serum enzyme concentration and the elevation of specific isoenzymes and other positive enzymatic changes, it can be clearly diagnosed as acute myocardial infarction. Cardiac blood pool imaging can be used to observe the dynamic image of contraction and diastole of ventricular wall, which has important reference value for determining ventricular wall motion and cardiac function.