There are many reasons for the vague pain in the left lung, such as pleurisy, costochondritis and so on. 1. Pleurisy: If there are diseases in the surrounding tissues of the chest or if the chest suffers from trauma, pleurisy may be induced, which may manifest as chest pain and cough, resulting in vague pain in the left lung. 2. costochondritis: pleural joints and ligaments can cause localized aseptic inflammation if they are damaged. Secondly, if the patient’s immunity is reduced, he may also be infected by pathogens, inducing costochondritis. The disease can cause vague pain in the left lung. There are many reasons for left lung pain, after the symptoms, we suggest that the patient go to the hospital in time to improve the examination, follow the doctor’s instructions to take standardized treatment, not to be ignored, so as not to delay the treatment.