Bilateral cochlear implantation is the latest trend in the world, which has the following advantages: 1. Better sound localization ability: with bilateral cochlear implantation, the localization accuracy of sound is more than doubled, and the ability to perceive the sound environment is greatly improved. 2. Improved speech recognition in noisy environments: some literature reports that speech recognition in noisy environments increases 9 times after the second side implant is implanted. Better interaction can be achieved in social activities. 3.Ensure that always the better hearing ear receives the implant. At the same time, if one side of the cochlear implant does not work, the patient will not be unable to hear. 4.Sound balanced input, listening easier and feel good 5.Maintaining and stimulating the auditory pathway on both sides 6.Bilateral implantation can be done in one surgery, saving cost.