The incidence of brain metastases in cancer patients is 15-30%, accounting for about 16% of intracranial tumors, and our center accounts for 23% of various intracranial tumors treated with stereotactic radiation therapy. Therefore, the incidence of brain metastases is not only on the rise in today’s human society, but also has become a major disease that poses a serious risk to life. Brain metastases tend to occur between the ages of 40 and 60, with the majority of metastases in the supratentorial frontal, temporal, parietal and occipital lobes, followed by the inferior cerebellar hemispheres. Metastases are classified as single, multiple or diffuse, with multiple common. Brain metastases are fast-growing, with early and severe tissue reaction, short course, and acute progression of clinical manifestations, and the natural average survival of untreated patients is 1 to 3 months. Lung cancer is the most common primary cancer site of brain metastases, followed by breast cancer, gastrointestinal cancer, urological cancer and malignant melanoma. I. Treatment effect Stereotactic radiation therapy for brain metastases generally relieves the symptoms in 2 to 4 weeks of treatment, and the tumor is reduced or disappears after 3 months, with the control rate of tumor above 90%, and the average survival period is 10 to 14 months. Treatment methods The purpose of treatment is to prolong the survival period of patients and improve the quality of survival. At present, the indications of radiosurgery (stereotactic radiotherapy) for the treatment of brain metastases are: 1, the diameter of metastases ≤ 30 mm, multiple metastases, can be preferred to stereotactic radiotherapy treatment; 2, the diameter of metastases ≥ 30 mm single foci / or multiple foci, can be first surgical removal of the occupying effect, and then stereotactic radiotherapy treatment [2]; 3, diffuse metastases, first 3, diffuse metastases, firstly, stereotactic radiotherapy treatment, followed by whole brain radiotherapy; 4, cases of recurrence after surgery and radiotherapy, generally choose stereotactic radiotherapy treatment; 3, treatment-related problems and countermeasures Brain metastases account for the largest percentage of (intracranial) malignant tumors treated by stereotactic radiotherapy, about 75% in our center. Since brain metastases have clear borders and regular morphology, they have good requirements for targeted tumor treatment. At the same time, brain metastases do not require high radiation dose and produce little radiation reaction/or damage after treatment. Diffuse tumor foci, especially those with metastases of different sizes, are suitable for stereotactic radiotherapy followed by whole brain radiotherapy to address the limitations of stereotactic radiotherapy treatment. Stereotactic radiation therapy is very suitable for the treatment of tumors with a diameter of 30 mm and tumors located in tissue structure sensitive areas (functional areas). Stereotactic radiation therapy is limited by the total dose per exposure, otherwise the tissue response is severe and not conducive to improving the quality of survival, in which case whole brain radiation therapy must be added. Whole brain irradiation should be avoided as much as possible to protect the brain, especially sensitive tissues, which is the basis for improving the quality of survival. Brain metastases often require a combination of surgery, stereotactic radiotherapy, general radiotherapy and chemotherapy, but it should be noted that more and more cases and the literature are responding to the need to beware of the resulting side effects and the superposition of complications. It should be noted that there is a clinical trend of treatment transition and an increasing tendency of neglecting multiple treatment methods. We advocate that those who are suitable for stereotactic radiotherapy treatment should first undergo stereotactic radiotherapy treatment, followed by elective radiotherapy and chemotherapy. Stereotactic radiotherapy treatment only takes 3 hours, while radiotherapy requires 4 weeks or more than 4 months. After radiotherapy is finished, the patient’s brain metastases have developed and the systemic condition has decreased, and then stereotactic radiotherapy treatment will increase the risk of tissue reaction and complications. Therefore, we emphasize the sequential arrangement of stereotactic radiotherapy and radiotherapy, and the rhythm of various treatment arrangements. Stereotactic radiation therapy for brain metastases is related to the following factors: 1. size of tumor and number of tumors: if the tumor volume is small and the occupying effect is light, the treatment effect and prognosis are better; if the number of tumors is more than 6~8, diffuse distribution, and the tumor size is different, the treatment effect and prognosis are poor. 2.Tumor site: tumors located in cortical functional area, basal ganglia, brainstem or large tumors located in posterior cranial fossa have poor treatment prognosis. 3.Brain metastases after radiotherapy have low sensitivity to stereotactic radiotherapy and many tissue reactions and complications. 4.The prognosis of stereotactic radiotherapy treatment is poor for those whose carcinoma in situ has not been investigated, or whose carcinoma in situ has not been effectively treated. 5.The prognosis of stereotactic radiation therapy treatment is poor for those who are old, have poor general condition (Kpa’s score <60< span="">), severe anemia, or combined with systemic organ organic diseases.