Multiple solid nodules in the upper lobe of the left lung are lung imaging tests such as chest CT suggesting multiple dense shadows in the upper lobe of the left lung, which may be caused by pneumonia, tuberculosis and tumors. 1. Pneumonia: it may be due to inflammation of the left lung caused by various bacterial, viral and fungal infections, which will cause symptoms such as chest tightness, chest pain, cough, sputum, fever, etc. Multiple solid nodules appear because of inflammatory exudation and fibrous tissue proliferation. 2. Tuberculosis: due to Mycobacterium tuberculosis infection, manifested as cough, sputum, low fever, night sweats, etc. Because of the erosion of Mycobacterium tuberculosis and its metabolites, there are multiple solid nodules in the upper lobe of the left lung. 2. Tumor: the most important thing to be excluded is lung tumor, diffuse alveolar carcinoma or metastasis caused by other tumors will cause multiple solid nodules in the upper lobe of the left lung. The presence of multiple solid nodules in the upper lobe of the left lung requires prompt medical attention, and further investigation and treatment as prescribed by the doctor.