There are approximately 120 million people with hearing disabilities worldwide, and the population of people with hearing and speech disabilities in China amounts to 20.57 million. With no ideal conservative cure for sensorineural hearing loss, the main intervention method is to wear hearing aids and cochlear implants, which are suitable for most patients. Hearing aids are a vital and indispensable intermediate link in the chain from diagnosis to rehabilitation of hearing loss. The function of a hearing aid is to amplify sound to a degree and in a manner that allows the hearing impaired person to communicate effectively using residual hearing. Commonly used hearing aids can be divided into the following categories according to their appearance and wearing position: 1. Behind-the-ear hearing aids: It is a hearing aid that relies on a hard plastic ear hook that is bent in a semi-circle and hung behind the ear. There are volume knobs and program control knobs on the back of the machine, both low-powered and high-powered, which are suitable for patients with various hearing losses. 2. In-the-ear hearing aid: It is the earliest customized hearing aid developed and applied. It occupies the earnail cavity and the earnail boat, and its shell is customized according to the shape of the patient’s earnail, which makes it more solid and comfortable to wear. It is more in line with the natural position of the human ear to feel the sound than the behind-the-ear hearing aid. 3.Canal hearing aid: slightly smaller than in-the-ear hearing aid, it is one of the more popular hearing aids at present. It can be placed deeper into the ear canal. The shell of the hearing aid can be customized according to the color of the skin, thus making it more discreet. 4.Completely in-the-ear hearing aid: It is the smallest hearing aid at present. It is not easy to be found even from the side, and its amplification characteristics are closer to the physiological characteristics of the normal human ear. Hearing aid fitting requires systematic and standardized assessment and analysis by clinicians, audiologists and audiologists in order to obtain good results.