In infancy, it is necessary to hear the sounds around the child before the child can imitate the sounds and babble. For those children who lose their hearing before they are exposed to sound, they often lose their ability to express themselves verbally at the same time, so such children become deaf and mute, which is typical of prelingual deafness. After such a child is fitted with a cochlear implant, there is a corresponding transmission of sound signals, but since the child has never been exposed to sound, he or she may not be able to respond to the sound signals produced by the cochlear implant. However, as the child’s hearing and speech develops, normal hearing and speech can be developed with the help of a cochlear implant. However, the recovery time and difficulty of prelingually deaf children with cochlear implants is closely related to the age at which the cochlear implant is fitted. 1-3 years old is the peak age of speech development in young children, and the younger the cochlear implantation age, the better the functional recovery will be. The younger the age of the cochlear implant, the better the functional recovery. For example, before the age of 1 year, the child is just beginning to babble. If the cochlear implant is implanted at this time, and the child starts babbling like a normal child of the same age, then the recovery time is not much different from that of a normal child, or even no different. If the cochlear implant is implanted at a later age, such as 3-5 years old, when the child has already missed the best period of language development, and normal children of the same age have already learned to speak, then the patient’s recovery of speech will take longer, and the difficulty of recovery is also greater. Therefore, the younger the age of implantation, the shorter the time of deafness and the less difficult the rehabilitation; on the contrary, the older the age of implantation, the longer the time of deafness and the more difficult the rehabilitation. This means that the optimal age for cochlear implantation is around 1 year old. In short, a cochlear implant can be considered when the child is half to one year old and weighs eight kilograms or more. As for patients with post-speech deafness, that is, adults or children who can already speak before the onset of the disease and are able to produce a normal response to sound. After the cochlear implantation, when the machine starts to work, since the sound heard by the patient through the cochlear implant may be different from normal hearing, there is a process of familiarization and learning of the cochlear implant’s sound after the implantation of the cochlear implant to gradually understand the language and then learn to speak. After the necessary training and familiarization process, most implanted patients can understand other people’s speech and participate in daily conversations.