It is very likely that lung nodule 20mm is early stage lung cancer, but to clarify whether it is early stage lung cancer or not, it needs to be further combined with a variety of auxiliary examinations to make a judgment. When the diameter of lung nodule is ≥8mm, it is necessary to improve bronchoscopy, CT enhancement scan, PET/CT scan, percutaneous lung puncture biopsy to clarify whether it is lung cancer. After clear diagnosis, abdominal CT, bone scan, head nuclear magnetic enhancement examination, lymph node ultrasound and other examinations are also needed to determine whether there are distant metastases in order to stage the lung cancer. Surgical treatment is preferred for those who are highly suspected to be malignant and suitable for surgical treatment. If the examination result shows a lung nodule of 20mm, one should improve other examinations with the help of doctor to make a clear diagnosis, build up confidence in treatment, and carry out treatment as early as possible.