The need for chemotherapy after lung cancer surgery is determined by the condition of lymph node metastasis, the condition of the cut edge and the degree of pathological differentiation. Generally for early stage lung cancer, patients do not need chemotherapy after surgery. And the main reasons why chemotherapy is needed after lung cancer surgery commonly include patients with general primary tumor diameter of 3cm or more in tumor and postoperative metastasis of hilar and mediastinal lymph nodes, patients with positive postoperative cut margin, and adenocarcinoma, squamous carcinoma or special type of carcinoma with relatively low pathological differentiation, all need chemotherapy.