The skull is a relatively hard bone outside the brain that protects the internal tissues of the brain as well as the nerves, but it is still susceptible to cranial defects when subjected to violent external injuries, such as a traffic accident or a fall from a high speed, caused by debridement decompression. What are the dangers of cranial defects? Patients with cranial defects are in need of cranial repair surgery, mainly because the shape of the cranial defect area is changed and the scalp is affected by atmospheric pressure, which causes it to involute and compress the brain tissue. Patients often have a heavy burden of thoughts such as insecurity and can cause syndromes such as headache, dizziness and fear of vibration. The longer the skull defect, the higher the incidence of skull defect syndrome and secondary brain damage. Cranial repair experts say that in order to restore the cranial cavity confinement, keep the physiological intracranial pressure stable, and reduce the cranial defect syndrome, cranial repair should be performed for cranial defect diameter above 3 cm, without muscle coverage and without contraindications, and the operation time is usually chosen between three months and six months after craniotomy. The choice of material for cranial repair is also very important to effectively reduce the infection rate and rejection reactions. We use the new PEEK material for cranial repair. PEEK (polyether ether ketone) has many advantages such as high temperature resistance, corrosion resistance, sturdiness, and good toughness at the same time, and does not interfere with postoperative review. PEEK material is generally shaped using 3D printing technology for overall shaping and fusion casting, so it can be personalized and perfectly shaped according to the patient’s cranial defect site. Furthermore, PEEK significantly reduces the rate of subcutaneous fluid accumulation and subcutaneous infection after surgery.