The causes of pulmonary nodules are many, the more common clinical causes are infections, including bacterial infections, viral infections, fungal infections and tuberculosis infections, etc., but also seen in related benign tumors, malignant masses, and a history of related lung diseases. 1. Infectious factors: the more common is caused by bacterial infection of pneumonia, tuberculosis foci due to tuberculosis infection, in addition to fungi, viruses can also lead to lung infections, in the presence of inflammation, neutrophils and other secretion of fibrin, the inflammatory foci of the parcel, and then the formation of lung nodules. 2. Benign tumors: the more common ones in the clinic are lung malformation tumor, lung calcification nodule, etc., which can be manifested as lung nodule on imaging. 3. Malignant tumors: such as lung adenocarcinoma, lung squamous cell carcinoma, etc. The imaging of the cancerous foci may be manifested as lung nodular foci. 4. History of lung diseases: for patients who have suffered from related lung diseases in the past, scar tissue can be formed in the lungs, such as tuberculosis, lung trauma, etc., which can be manifested as lung nodules. There are other causes of pulmonary nodules, such as heredity, environmental factors, smoking, etc. Patients are advised to seek timely medical attention to avoid delaying their condition.