Partial solid nodule 23mm in the left upper lobe of the lung has a higher probability of being malignant, if the nodule is malignant it is more serious, if it is caused by benign disease it is usually not serious. Lung nodules can be categorized into solid nodules, pure ground glass nodules, and partially solid nodules according to their density. Partially solid nodules are nodules that have both a solid and a ground glass component and have a high likelihood of malignancy, about 63%. Nodule size is also associated with the risk of malignancy, with the larger the nodule the higher the risk of malignancy, so a 23 mm partially solid nodule in the left upper lung has a high risk of malignancy. If it is caused by malignant tumors such as bronchopulmonary cancer and metastatic lung cancer, it is serious, and lung cancer, etc. can affect the quality of life and endanger life; the nodule also has a certain possibility to be caused by lung misshapen tumors, rheumatoid nodules, and pneumonia, etc. If it is a benign nodule, it can usually be improved or cured by timely treatment. The risk of malignancy of lung nodules needs to be fully evaluated in terms of morphology, margins, blood supply, etc. Patients are advised to consult a specialist and follow the doctor’s instructions for further examination and treatment.