Lung hemorrhage may be caused by bleeding from the upper respiratory tract such as the nose and gastrointestinal tract that is accidentally aspirated into the airways, inflammatory lung disease, lung cancer, pulmonary embolism, and left heart failure. 1. Bleeding from the rest of the body: the cause of pulmonary hemorrhage needs to be excluded from the possibility of bleeding from the upper respiratory tract such as the nasal cavity and gastrointestinal tract being mistakenly aspirated into the airways. 2. Inflammatory diseases of the lungs: bacterial infection and fungal infection of the lungs can lead to diffuse damage to the alveoli and hemorrhage, hemoptysis and other symptoms. 3. Lung cancer: the main types of lung cancer are small cell lung cancer and non-small cell lung cancer, which can cause damage to lung tissues and lead to pulmonary hemorrhage. 4. Pulmonary embolism: embolism of blood vessels in the lungs leads to increased resistance of pulmonary circulation, overfilling of pulmonary blood vessels, blood leakage into alveoli and bronchial tubes, and finally coughed up through the trachea. 5. Left heart failure: left ventricular compensatory insufficiency, resulting in pulmonary hypertension, blood into the alveoli, manifested by dyspnea, cough, cough pink foamy sputum. Lung hemorrhage may also have other causes, such as bronchiectasis, pulmonary vasculitis, tuberculosis, trauma such as lung contusion, rib fracture puncture. It is recommended to go to the hospital in time, complete the examination, and give the diagnosis and treatment after clarifying the cause of the disease.