Hidden pain in the left lung may be due to pneumonia, lung cancer, pulmonary embolism, angina pectoris, reflux esophagitis, etc., which needs to be treated medically or surgically for the cause. 1. Pneumonia: After bacteria, mycoplasma, chlamydia and other types of pathogenic microorganisms infect the left lung tissue, resulting in inflammatory reaction in the lung, local inflammation and exudation cause this symptom. The patient can use ceftazidime, moxifloxacin, azithromycin, erythromycin and other medicines as prescribed by doctor for anti-infection treatment. 2. Lung cancer: In middle and late stage, left-sided lung cancer causes this symptom due to malignant proliferation and local invasion of cancer cells, which leads to destruction of normal tissues and stimulation of nerves of chest wall. It can be treated by surgery with radiotherapy, immunotherapy and targeted therapy. 3. Pulmonary embolism: after the thrombus of deep vein of lower limb and fat tissue enter into pulmonary artery and its branches, resulting in narrowing and obstruction of pulmonary artery, pulmonary embolism may appear in some peripheral pulmonary embolisms, which may cause hidden pain in lungs. Warfarin, heparin, rivaroxaban and other drugs should be taken as prescribed by the doctor for anticoagulation or thrombolytic therapy such as urokinase, and those with serious conditions should undergo emergency intervention or surgical treatment. 4. Angina pectoris: various factors lead to coronary artery stenosis, limitation of blood supply to the heart, myocardial ischemia and left anterior thoracic pain, which is mistaken for left lung pain. Nitroglycerin, aspirin, clopidogrel, resuvastatin and other drugs should be taken as prescribed by the doctor. 5. Reflux esophagitis: stomach acid and other gastric contents retrograde into the esophagus, resulting in esophageal erosion of ulcers, erosions and other changes, mistaken for hidden pain in the left lung. Omeprazole, ranitidine, domperidone, aluminum phosphate gel and other drugs should be taken as prescribed by the doctor. It is recommended that patients seek timely medical attention to clarify the cause of the disease and provide targeted treatment. Drugs should be used under the guidance of a doctor, avoid self-medication.