Patients with left-sided pain under the ribs, the following causes are common: First, trauma: such as rib fracture, intercostal muscle injury and intercostal nerve injury, can cause pain under the left ribs, and can be accompanied by local swelling, restricted respiratory activity, serious will be accompanied by hemothorax and pneumothorax, generally through X-ray examination, CT scan examination can confirm the diagnosis. Secondly, bronchopneumonia or lung tumor: it can cause pain under the left rib cage, the pain is not obvious in the early stage of the tumor, but in the middle and late stage, the pain will be more serious, usually ordinary pain medication is difficult to relieve, the patient will also be accompanied by coughing, coughing sputum, serious cases will also appear general weakness, fever and other clinical symptoms, through CT scan or MRI can confirm the location of the lesion. Early diagnosis and treatment can provide rapid relief of the pain below the left rib cage, but if treatment is delayed, it may even affect the patient’s normal life.