Coughing up blood is a symptom, which is manifested as blood in sputum, sudden coughing up blood, coughing up blood in large quantities, etc. It is common in bronchitis, bronchial lung cancer, bronchial tuberculosis and other diseases. 1. Bronchitis: After the bronchial mucosa is stimulated by bacteria, viruses and other pathogens, the inflammatory cells erode the capillaries and cause rupture, resulting in coughing up blood; or the bronchial tubes are dilated because of inflammation anyway, which causes irritating coughing and rupture of blood vessels, and coughing up blood will be caused as well. Usually the amount of bleeding is not much, which is manifested as sudden coughing up blood, sputum with blood and other symptoms. 2. Bronchopulmonary cancer: when the tumor is close to the main bronchus, when the tumor grows gradually and invades the local small blood vessels, it will lead to rupture of blood vessels and cause hemoptysis; or the tumor itself grows too fast and causes the tumor to collapse, then coughing up blood or coughing up sputum with blood, and part of the patients will have a large amount of hemoptysis due to excessive bleeding. 3. Bronchial tuberculosis: due to the stimulation of inflammatory reaction of tuberculosis foci and toxins on the wall of bronchial hair vessels, the permeability of hair vessels increases, and blood in sputum or bloody sputum appears after extravasation of erythrocytes; secondly, when tuberculosis foci collapsed by necrosis and eroded to the wall of blood vessels, then coughing up blood can occur. There are many other diseases can cause patients to cough up blood symptoms, the performance is more complex, should be timely to the hospital examination and treatment as prescribed by the doctor, so as not to delay the condition.