There are many main causes of small nodules in the lower left lung, most of which are due to benign tumor diseases such as old tuberculosis and inflammatory lymph node hyperplasia. If the area of the patient’s left lower lung nodule is not very large after examination, if it is below 1mm it can be ignored, most of these small nodules belong to benign tumors. If a patient has a left lower lung nodule with an area of about 2-3mm, he or she should go to the hospital for an annual review. If a patient has a left lower lung nodule with a diameter of more than 4mm, he or she needs to be followed up dynamically in the hospital and go to the thoracic surgery department or the respiratory department in a timely manner once the nodule is found to be increasing in size. If the nodule increases in size within a short period of time, the nodule becomes unclear at the edges and the surrounding lymph nodes are enlarged, it may be a sign of early stage lung cancer, which requires timely diagnosis and surgery if necessary.