The biggest risk of aneurysm craniotomy is the re-rupture and bleeding of the aneurysm, because in the process of aneurysm craniotomy clamping, it is easy to stimulate the surrounding neurovascular, and even directly will stimulate the aneurysm, if the operation is not careful, even 1mm difference, it may make the aneurysm rupture and bleeding again. And in the process of surgery, once the rupture and bleeding, the consequences are catastrophic. Sometimes the bleeding is so ferocious that there is no time to observe it, so it can only be palliative treatment, so it is the biggest threat. There are also cases, such as clamping too many blood vessels, causing blockage of blood vessels, ischemic necrosis of the nerves at the end, the risk of forming cerebral infarction, or after opening the skull, outside bacteria will enter the skull, thus creating the risk of intracranial infection, and there may be damage to the parenchymal part of the brain, thus creating the possibility of epilepsy, many situations may lead to the risk of surgery.