Generally, before cochlear implantation, patients who have the conditions should have a hearing aid trial process (3 to 6 months). After cochlear implant surgery is determined, some detailed preoperative examinations are required, which include: 1. Medical routine examinations: including etiological examinations of otologic history; routine otologic examinations (to exclude otitis media and eustachian tube lesions); imaging examinations (CT and MRI) (to understand whether the middle ear, the inner ear whether cochlear deformity fibrosis or ossification, internal auditory canal stenosis or occupancy to determine the integrity of the auditory nerve and pathways); general condition examination, because the surgery is performed under general anesthesia, so it is necessary to understand the patient’s heart, lung, liver and kidney function as well as some laboratory tests to see if they can tolerate the surgery. 2.Audiological examination: including pure tone audiometry or sound field test, speech audiometry, ABR, multi-frequency steady state, otoacoustic emission and acoustic conductance resistance, electrical stimulation test of the drum head, etc. 3. Psychiatric examination: Adult patients should be mentally and psychologically healthy, have a strong demand to accept the cochlear implant, be able to insist on post-operative rehabilitation training, and have a correct understanding of the role and effects of the cochlear implant. Children need the active cooperation of their parents.