Pulmonary nodules of 5.5 mm require comprehensive judgment and dynamic follow-up depending on the nature of the nodule. There are 3 types of pulmonary nodules: ground glass nodules, partially solid nodules and solid nodules. If a 5.5mm nodule is a ground glass nodule, it is mostly a benign chronic inflammatory infectious nodule. If there are no clinical symptoms, no special treatment is needed, only dynamic follow-up of high-resolution CT of the chest once a year is required. If a 5.5 mm nodule is a partially solid nodule, because it is the most malignant nodule, dynamic follow-up of the growth changes of this nodule is required. If a 5.5mm nodule becomes 6-8mm or even more than 8mm, especially with changes of early lung cancer such as short burr, lobulated, pleural traction sign and pleural depression sign, further enhanced CT chest examination needs to be given. If necessary, percutaneous lung aspiration cytologic biopsy should be given to clarify whether early lung cancer has occurred as early as possible, and if necessary, the thoracic surgeon should be asked to perform early surgery to remove the lesion.