For severe or profound deafness in both ears, the lesion site localization is diagnosed in the cochlea, cochlear implantation can be chosen. 1, prelingually deaf patients selection criteria: ① binaural severe or very severe sensorineural deafness; ② the best age should be 12 months ~ 5 years; ③ with appropriate hearing aids, after hearing rehabilitation training 3 ~ 6 months after the auditory language ability does not improve significantly; ④ no contraindications to surgery; ⑤ family and/or implantation of their own cochlear implantation of a correct understanding of the appropriate expectations; ⑥ hearing and speech rehabilitation education conditions. conditions. The younger the patient is at the time of surgical implantation, the better the outcome, which maximizes the potential for avoiding auditory sensory deprivation and expanding speech and language skills before the critical period of brain plasticity. Children or adolescents older than 6 years of age need to have a basic level of hearing and speech, a history of hearing aid wear and a history of hearing or speech training since childhood. Ineffective or very ineffective hearing aids are defined as open phrase recognition of ≤30% or two-word word recognition of ≤70% in the best hearing aid listening environment. Selection criteria for post-speech deafness patients: ① post-speech deafness patients of all ages; ② severe or very severe sensorineural deafness in both ears; ③ ineffective or very ineffective hearing aids, open phrase recognition rate ≤ 30%; ④ no contraindication to surgery; ⑤ good psychological quality and subjective initiative, with a correct understanding of cochlear implants and appropriate expectations; and ⑥ support from the family. The age of onset and duration of deafness in patients with postlingual deafness are closely related to the outcome after surgery. Generally speaking, those with early age of onset and longer duration of deafness have poorer outcomes after surgery. In addition, the listening environment in life and work after surgery can also affect the effect of cochlear implantation. 3, contraindications to surgery: ① absolute contraindications, including cases of severe malformation of the inner ear, such as Micheal malformation, no cochlear malformation, etc.; auditory nerve defects; severe mental retardation; unable to cooperate with language training; serious mental illness; acute and chronic inflammation of the middle ear mastoid has not been cleared; ② relative contraindications, including poor general condition; uncontrollable epilepsy; no reliable rehabilitation training conditions. Secretory otitis media and glue ear are not contraindications to surgery. Chronic otitis media with tympanic membrane perforation can be selected for one-stage or staged surgery if the inflammation is controlled. Stage I surgery is defined as radical treatment of the middle ear mastoid lesion, tympanic membrane repair (or mastoid cavity temporalis muscle tamponade and closure of the external auditory canal) along with cochlear implantation. Staged surgery involves removal of the lesion, repair of the tympanic membrane perforation or closure of the external auditory canal, followed by cochlear implantation 3-6 months later.