The classification of interstitial pneumonia is generally divided into known cause interstitial pneumonia, idiopathic interstitial pneumonia, granulomatous interstitial lung disease and rare interstitial lung disease. 1. Interstitial Pneumonia with known cause: Generally, there are allergic pneumonia, drug-induced interstitial pneumonia, connective tissue disease-associated interstitial pneumonia, pneumoconiosis and so on. 2. Idiopathic interstitial pneumonia: (1) Common idiopathic interstitial pneumonia: generally there are idiopathic nonspecific interstitial pneumonia, idiopathic pulmonary fibrosis, respiratory bronchiolitis with interstitial lung disease, desquamative interstitial pneumonia, cryptogenic mechanized pneumonia, acute interstitial pneumonia and so on. (2) Rare idiopathic interstitial pneumonia: idiopathic lymphocytic interstitial pneumonia, pleuropulmonary parenchymal elastofibroplasia, unclassified idiopathic interstitial pneumonia, etc. 3. granulomatous interstitial lung disease: nodular disease. 4. Rare interstitial lung diseases: pulmonary lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, chronic eosinophilic pneumonia, alveolar protein deposition, etc. It is recommended to consult a doctor in time, improve the lung CT, blood routine and other examinations and tests, and rational treatment under the guidance of the doctor.