Lung cancer metastasis refers to the invasion of cancer cells from the lung into blood vessels, lymphatic vessels or body cavities, where the cancer cells run with blood or body fluids and can take up residence in distant sites or organs, and then proliferate to form the same type of cancer foci as the primary cancer. Therefore, lung cancer metastasis must meet two conditions: ① The site of occurrence must be the distant part of the primary lung cancer. ② The cell type of cancer must be the same as that of the primary lung cancer. Lung cancer metastasis marks the spread of malignant tumor, which can cause greater and more extensive harm to the organism. Lung cancer is easily metastasized, and even metastases are found first before the primary site is found. The extensive metastasis of lung cancer is the main reason why it cannot be cured. Lung cancer often metastasizes in four forms: ① lymphatic tract metastasis; ② bloodstream metastasis; ③ direct local spread; ④ local transplantation. Metastases from different parts of lung cancer often bring great pain to patients and even threaten their lives, such as brain metastasis, bone metastasis, liver metastasis, spinal cord metastasis, mediastinal lymph node metastasis, superior vena cava syndrome, esophageal compression, pericardial metastasis and pleural metastasis. In conclusion, lung cancer metastasis is often a manifestation of advanced lung cancer, and the viciousness of the disease greatly reduces the patient’s quality of life and shortens the survival period. For advanced lung cancer, comprehensive treatments such as chemotherapy, radiation therapy, biological therapy and Chinese medicine can prolong the survival of patients.