How long can a patient with advanced lung cancer brain metastasis start to vomit live is uncertain, which is mainly related to the patient’s general condition and therapeutic effect and other factors. Vomiting in patients with brain metastasis of lung cancer is due to the occupying effect of tumor metastasis and the edema of surrounding brain tissues triggered by tumor lesions, thus resulting in increased intracranial pressure and symptoms such as headache and vomiting. If the patient’s general condition is good, the patient’s survival period is about 6-12 months if the patient is treated with drugs to actively reduce intracranial pressure and dehydration. If the condition progresses and the tumor metastases gradually increase in size, causing brain hernia, then the patient may experience respiratory and cardiac arrest at any time. Therefore, lung cancer patients should go to regular hospitals in time, follow the diagnosis and treatment advice of specialists, actively cooperate with the treatment, and follow up regularly. If the disease progresses and brain metastasis occurs, patients should cooperate with specialists in time to prolong the survival time.