With the rapid increase in the number of cases of brain tumor treated with gamma knife, it is not uncommon that the symptoms worsen after gamma knife treatment, and the tumor needs to be removed by craniotomy after longer conservative treatments such as dehydration, hormone and shunt are ineffective. The reason is that the volume of brain tumor will not shrink or disappear rapidly after gamma knife irradiation, furthermore, gamma radiation can cause tumor tissue edema, hemorrhage, necrosis, as well as the destruction of the blood-brain barrier and other factors can lead to an increase in tumor size, resulting in increased intracranial pressure and brain nerve damage signs and even brain herniation. The following factors should be considered when performing gamma knife treatment: ① The size of the brain tumor. Brain tumors with a diameter of 25-30 mm or less should be selected, and larger brain tumors should be surgically removed. For those located in important functional areas, in order to avoid serious postoperative neurological dysfunction, total excision is not forced, and the residual part can be treated with gamma knife. ②Site of brain tumor. If the lesion is located in the midline or posterior cranial recess and has caused obstruction of the cerebrospinal fluid circulation pathway, the tumor should be removed surgically or a cerebrospinal fluid shunt should be performed to relieve the compression and obstruction, and then gamma knife treatment should be performed, and the residual tumor that cannot be removed surgically can be treated with gamma knife again. ③The nature of brain tumor. Benign brain tumor should be removed as far as possible, malignant glioma surgery is difficult to completely remove, gamma knife can be used as one of the measures of comprehensive treatment. ④The degree of cerebral edema. If the tumor and the surrounding brain edema are serious, adequate internal and external decompression should be operated first, and postoperative adjuvant gamma knife treatment. Gamma knife is one of the very effective methods to treat brain tumor, but gamma knife cannot replace surgery. Especially when the tumor is located in the posterior cranial fossa, it is easy to affect the cerebrospinal fluid circulation and compress the brainstem, and the volume of the compensated posterior cranial fossa is smaller than that on the curtain, and the reaction to radiotherapy is also more serious. Therefore, once brain tumor causes cranial nerve damage or combined with increased cranial pressure, surgery should be the first choice. Cheng Haimin, Department of Radiotherapy, Armed Police General Hospital