Secondary tuberculosis of the left lung is a specific diagnosis of tuberculosis, a pathological description seen by CT or X-ray chest films of both lungs, which is the active type of tuberculosis, extremely contagious, commonly of the fibrous cavity type of the left lung, even accompanied by compensatory emphysema and pulmonary atelectasis. Patients may have symptoms of tuberculosis, such as wasting, weakness, chest tightness, wheezing, shortness of breath, and persistent low-grade fever. The patient should be treated as early as possible with systematic and standardized combination of anti-tuberculosis drugs, and be given appropriate bed rest, enhanced nutrition and a high-protein diet.