Whether a left upper lobe ground glass nodule is serious or not needs to be decided based on the size and nature of the nodule. If the left upper lobe ground glass nodule is less than or equal to 5mm or less, regardless of benign or malignant nodule, it can be temporarily observed, so it is not very serious. If the nodule is less than or equal to 8mm, it indicates that the nodule has a developmental trajectory, and it is necessary to determine whether it is a malignant nodule according to the morphology, location, density and other characteristics of the nodule, and if it is a malignant tumor, it is generally more serious. Therefore, patients with ground-glass nodules on the left lung are recommended to go to the hospital for further examination, and according to the results of the examination, if the nodules are found to have increased in size, they should be treated through surgical resection in a timely manner.