Generally, 3mm to 5mm lung nodules are benign, but not absolutely, need to go to the hospital for diagnosis and clarification. Lung nodules are relatively common in clinic, and there are many causes of lung nodules, such as long-term smoking, tuberculosis, environmental factors and so on. However, if the nodules are realistic, it is necessary to consider whether they are caused by cancer. Generally speaking, if the lung nodule is smaller than 5mm, it is more likely to be benign, but it is not certain. According to the clinical symptoms, nodule morphology and changes, it is necessary to decide whether it needs to be examined by pathology. Oral antibiotic treatment can be followed by review. If there is no change or the nodule becomes smaller, and inflammation is considered to be the cause, then conservative treatment can be used, but regular review is required. If there is obvious change of the nodule or changes such as burr sign are found in the review, then lung cancer is considered as a possible cause, and the nature of the lesion should be clarified in time and surgical treatment should be carried out. It is recommended to go to the hospital for diagnosis in time and give corresponding treatment plan.