The causes of subpectoral pain include digestive system diseases, cardiovascular system diseases, respiratory system diseases and skeletal system diseases. 1. Digestive system diseases: such as gastric ulcer, gastritis, reflux esophagitis, etc., can lead to subpelvic pain, mostly accompanied by acid reflux, belching, gastric distention and other indigestion symptoms. 2. Cardiovascular diseases: such as myocardial ischemia, coronary artery stenosis or occlusion, manifested as chest pain, tightness in the chest, most of them are crushing pain. 3. Diseases of the respiratory system: such as pneumonia, inflammation involving the pleura will appear chest pain, chest tightness and other symptoms, mostly accompanied by coughing, coughing and other discomforts. 4. Skeletal system: such as the lower side of the sternum connected to the rib fracture, there will be localized pain, coughing or change position when the pain is aggravated, localized skin lesions or bruises can be seen. There are many other reasons for the pain in the lower side of the sternum, and it is recommended that the patient go to the regular hospital in time to avoid delaying the condition.