The common pulmonary tuberculosis lesions that cause hemoptysis are infiltration and exudation, various types of cavities and caseous pneumonia, acute hematogenous pulmonary tuberculosis with a small amount of hemoptysis. The bleeding mechanism is that tuberculosis increases capillary permeability and blood oozes, which is characterized by bloodshot, blood spots or small blood clots in sputum; If the lesion erodes small blood vessels and causes rupture, it will cause moderate hemoptysis; For example, the rupture of a small aneurysm formed by pulmonary artery branches in the lumen wall or the rupture of arteriovenous fistula formed by secondary tuberculous bronchiectasis can cause massive hemoptysis and even endanger life. The mechanism of hemoptysis caused by bronchial tuberculosis is mainly that inflammation damages bronchial mucosa or capillaries at the focus, which increases its permeability or breaks submucosal vessels, often caused by blood in sputum or a small amount of hemoptysis.