Brain metastases occur in about 30% of patients with tumors. Brain metastases are also the most common type of intracranial tumors. Common brain metastases whose primary tumors are: small cell lung cancer, lung adenocarcinoma, breast cancer, colon cancer, rectal cancer, malignant melanoma, foreign data reported that 1/2 of the patients are single metastases, 20% of the patients have two brain metastases. Certain brain metastases such as small cell carcinoma of the lung, prostate cancer, uterine cancer, gastrointestinal tract tumors are prone to occur in the cerebellum. Most of the metastatic tumors appear as spherical, well-defined solid masses. In addition to occupying effect, metastatic tumor can also destroy adjacent structures, and peritumoral edema is obvious. They present with two main symptoms: intracranial hypertension and localized symptoms, and in some cases, multiple, scattered small metastatic lesions of the leptomeninges are seen on MRI. According to Posner JB, the median survival of symptomatic brain metastases without treatment is 1 month. With hormonal therapy, the median survival is up to 2 months, and treatment prolongs survival and improves quality of life. Niederer et al. proposed the use of regression partition analysis (RPA) to evaluate patients for aggressive treatment, which refers to the use of surgery and radiosurgery. Surgical treatment is appropriate in single lesions with an unspecified diagnosis, if surgery is an option with low surgical risk, with a KPS score of at least 70, under 60 years of age, and who are expected to live for at least two months or more. Radiotherapy has a wide range of indications, regardless of single multiple lesions. With whole brain radiotherapy alone, 50% of patients have significant neurologic improvement, but radiotherapy-induced injury may occur after 1 year post-treatment in 10-20% of patients using this segmentation modality. Since most of the brain metastases have clear boundary, round shape, and radiobiological characteristics of early response tissues, they are especially suitable for radiosurgery with remarkable efficacy. Stereotactic radiosurgery has the advantages of no craniotomy, little trauma, and multiple lesions can be treated at the same time. For single, large (3-4cm), or metastatic tumors that are not sensitive to external radiotherapy, it is better to use gas pedal three-dimensional conformal intensity-modulated conformal radiotherapy. Fractionated treatment has the characteristics of non-invasive, convenient, wide therapeutic range and safer. After whole brain radiotherapy for brain metastases, the general survival is 3-6 months. For KPS greater than or equal to 70 points, primary tumor control, age less than 65 years old, the median survival is 7.1 months. For KPS <70 points, median survival is 2.3 months. Follow-up after radiotherapy for brain metastases ranged from 5-26 months, with local control rates of 73%-94%.