There are many causes of left subclavian pain, and the common ones are chest muscle strain, tuberculosis, pneumothorax, angina, and so on. 1. Chest muscle strain: due to excessive exercise or prolonged weight-bearing on the left upper limb, the left chest muscle is strained, resulting in pain. 2. Tuberculosis: Tuberculosis occurs due to the infection of tuberculosis bacillus, which is often manifested as coughing and sputum, and chest pain when tuberculosis foci involve the pleura, and left subclavian pain when the foci are in the left upper lung. 3. Pneumothorax: people with underlying lung diseases are prone to pneumothorax triggered by strenuous exercise, which often manifests as sudden chest pain, dyspnea, coughing and other symptoms, and left subclavian pain when the left lung is involved. 4. Angina pectoris: angina pectoris is caused by insufficient blood supply to the coronary arteries, and angina pectoris is often characterized by shortness of breath, chest tightness, chest pain and other symptoms. Angina is often characterized by shortness of breath, chest tightness, chest pain and other symptoms. Angina will be felt as left subclavian pain. There are other reasons for left subclavian pain, it is recommended to go to the hospital in time to identify the cause of the disease, targeted standardized treatment. In order to avoid delays in the condition.