It is a common symptom that can be caused by a variety of reasons, the most common causes are mainly the following three: first, cardiac causes, if the elderly, and the previous history of hypertension, coronary heart disease, etc., to highly suspect coronary angina, especially pain and activity related, early improvement of electrocardiogram, cardiac ultrasound clear diagnosis. Second, digestive system diseases, the most common is reflux esophagitis, the location and nature of pain is very similar to coronary heart disease, but not related to activity and the ECG is also normal, the patient is often accompanied by acid reflux performance, barium meal and gastroscopy can help to make a clear diagnosis. Third, respiratory diseases, such as pneumonia and pneumothorax, etc., but the pain is often related to breathing, the patient may also have fever, cough, sputum and other manifestations, chest CT can help clarify the diagnosis.