Undifferentiated lung cancer is a general term for a group of poorly differentiated lung cancers, which is highly malignant, grows rapidly, spreads easily, and develops extensive metastasis in lymphatic and blood tracts at early stage, which is a more serious disease and needs active treatment. Surgery can be considered for small cell lung cancer without lymph node metastasis and distant metastasis in early stage, while small cell lung cancer with lymph node metastasis and extensive metastasis should emphasize on radiotherapy and chemotherapy as the main comprehensive treatment, but it is easy to recur and metastasize after remission period. Large cell carcinoma has poor sensitivity to radiotherapy and chemotherapy, and its efficacy is worse than that of other types of non-small cell lung cancer in the same period. It is recommended that patients choose appropriate treatment methods under the guidance of doctors and actively treat the disease to avoid delay.