There are many reasons that can cause multiple pulmonary nodules, not necessarily all malignant. Multiple pulmonary nodules are commonly found in patients who have previously suffered from tuberculosis. If the lesions are not completely absorbed after standardized anti-tuberculosis treatment, they are prone to form proliferative nodular changes in the lungs, and the lesions do not easily disappear and form multiple pulmonary nodules, which are mostly benign. Long-term smoking and exposure to dust, including masons and coal miners. Long-term inhalation of dust containing silica in the lungs is prone to the formation of silicosis nodules, nodules are mostly benign. Some autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus, also tend to form multiple pulmonary nodules when lung damage occurs. In this case, the nodules are mostly granulomatous changes and are benign. A small number of patients with alveolar cell carcinoma are prone to form multiple nodules in the lungs, which are malignant and need to be examined by chest enhanced CT or PET-CT as early as possible. If necessary, fiberoptic bronchoscopy and alveolar lavage fluid should be given to find tumor cells to avoid leakage and misdiagnosis.