Cranial defects are a common condition in brain surgery. There are many causes of skull defects, and the common cause is trauma. Cranial defects are often accompanied by fractures of the zygomatic bone, maxilla, mandible, nasal bone or even multiple craniofacial fractures, which are difficult to repair. Cranial tumor removal and debridement and decompression surgery are also causes of cranial defects. The necessity of skull repair: skull injury not only affects aesthetics, but also brings insecurity to patients and even causes a variety of adverse consequences such as cranial defect syndrome, brain atrophy, and traumatic epilepsy. The scalp and dura mater not supported by the skull can compress the brain tissue under the direct action of atmospheric pressure, and the brain tissue without skull protection can be displaced with the change of body position for a long time, causing the change of blood circulation in the brain, or the subarachnoid space disappears due to the adhesive displacement of the scalp and dura mater, the cerebral cortical perfusion decreases, and the softening foci of brain tissue under the bone window increase, which can form traumatic cysts, cerebral penetration malformation, and ventricular asymmetry, etc. Therefore Cranial repair should be performed. The purpose of cranial repair: 1.improve the blood circulation of brain tissue; 2.improve the cerebrospinal fluid circulation of brain tissue; 3.release the adhesions at the cranial defect of brain tissue; 4.keep the stable pressure of brain tissue from changing with the external changes of air pressure.