Lung nodule severity in addition to judging according to the size of the nodule, should also be combined with the nature of the nodule to judge, 3mm nodule, if benign is not serious, if malignant, more serious, need to timely surgical resection. If the lung nodule is a simple solid nodule, and 3mm lung nodule is relatively small, the possibility of malignant nodule is low, if there is no accompanying obvious clinical symptoms, in general, are not serious, can be followed up once every 3~6 months to review, do not need to worry too much. If the lung nodule is found to be associated with vascular reconstruction on chest enhancement CT, the possibility of early carcinoma in situ should be considered, and it is recommended that it be resected after further examination and definitive diagnosis. If the nodule is found to have a tendency to increase in size during the review process, the possibility of malignancy should also be considered and early surgical resection is required. If a 3mm lung nodule is found, patients are advised to consult a doctor for professional advice.