Lung adenocarcinoma is a kind of malignant tumor of the lung, and the most important characteristics of malignant tumors distinguished from benign tumors are their invasiveness and metastasis. When lung adenocarcinoma develops to an advanced stage, the adenocarcinoma cells can enter into the brain by means of hematogenous metastasis. This is because there are some anastomotic branches between cerebral blood vessels and vertebral artery and jugular venous plexus supplying the brain, and adenocarcinoma cells can enter into the brain through blood line metastasis of these branches. There are two ways of brain metastasis, one is metastasis of brain parenchyma. One is parenchymal metastasis and the other is meningeal metastasis. Generally, parenchymal metastasis is accompanied by some symptoms of increased intracranial pressure or focal signs, while meningeal metastasis can have headache, nausea, vomiting and other symptoms of increased intracranial pressure. Once brain metastasis of lung adenocarcinoma occurs, it means that the lesion has reached stage IV, and the chance of radical surgery has been lost, and its treatment is comprehensive treatment mainly based on targeted therapy and chemotherapy.