Chemotherapy for brain metastasis of lung adenocarcinoma is effective, but due to the existence of blood-brain barrier, it is difficult for chemotherapeutic drugs to enter into the brain, and its therapeutic effect is limited. Brain metastasis of lung adenocarcinoma indicates that it is the manifestation of advanced stage of cancer, and lung adenocarcinoma is also prone to brain metastasis, etc. Chemotherapy and radiotherapy are the main treatment. If the brain metastasis lesion is more limited, brain surgery is also feasible to remove the metastatic tumor. If the patient’s condition is more serious, he/she may need to receive radiotherapy and chemotherapy to control the onset of the tumor, but it is not possible to stop the spread and metastasis fundamentally. While radiotherapy and chemotherapy kill tumor cells, they may also injure the body’s normal immune cells. Side effects may occur after chemotherapy, such as vomiting, anorexia, decreased immunity and hair loss. Therefore, chemotherapy can also be used in conjunction with targeted therapy to prevent cancer cells from spreading and metastasizing.