Occasional vague pain in the left side of the chest can be caused by angina pectoris due to myocardial ischemia, inflammation of the intercostal nerves, soft tissue injuries, gastritis or gastric ulcers. Pain in the left side of the chest, belonging to the chest pain of a situation, also need to be treated carefully, although the causes are more, but at any time may be life-threatening. Chest pain is strictly speaking, the diagnosis and treatment should consider the occurrence of pain triggers, pain each time the duration of time, the nature of the relief factors, etc. If the pain is in emotional excitement or strenuous activities, it may be coronary heart disease myocardial ischemia caused by angina pectoris. If there are no obvious triggering factors, no underlying diseases, and vague pain when calm, intercostal neuralgia may be considered; if the pain is pressed, it may be a soft tissue injury; and if the pain is related to dietary factors, digestive tract problems may be considered. Occasional vague pain in the left chest, if it always occurs, it is recommended to go to the hospital as soon as possible.