The causes of left-sided chest pain mainly include the following aspects: First, it is considered to be caused by heart diseases, including myocardial ischemia, myocardial strain and exertional angina, which can cause left-sided chest pain, and can be identified by performing electrocardiogram, ambulatory electrocardiogram and cardiac ultrasound. Secondly, it is considered to be caused by respiratory system diseases, including acute and chronic bronchitis, pulmonary alveoli, spontaneous pneumothorax, etc., which can cause vague pain on the left side of the chest, mostly accompanied by cough, wheezing and other respiratory symptoms. Thirdly, it is considered to be caused by intercostal nerve pain or chondromalacia, which is mostly caused by strenuous activities or limb lifting.