Most of the high-density shadow in the lung is not serious, because the high-density shadow is mostly due to lung infection, foreign body accidentally inhaled into the trachea, as well as the calcification foci formed after one of the diseases such as pulmonary tuberculosis healed, which shows high-density shadow under X-ray, and the condition is not serious. If there is afternoon hot flush, fever, cough, night sweats or blood in sputum, consider the recurrence of pulmonary tuberculosis, improve the diagnosis of tuberculosis smear and sputum bacterial culture plus drug sensitivity test as soon as possible, and give isoniazid, rifampin and pyrazinamide combination anti-tuberculosis treatment in time. If there is an isolated high-density shadow, it is necessary to be alert to lung tumor, and the diagnosis can be made by fibrinoscopy and thoracic aspiration biopsy, and surgical resection, radiotherapy and chemotherapy can be performed as soon as possible.