To investigate the etiology of deafness in Chinese deaf patients, the Molecular Diagnostic Center for Deafness of the PLA General Hospital conducted a survey on the etiology of deafness in 134 deaf patients in a typical region of northern China, including medical history questioning, hearing tests, otologic examination, and deafness genetic testing. The etiological composition of deaf patients in this region was analyzed and divided into nine categories, as shown in Fig. The proportion of deafness related to genetic factors in the region reached 60.45% (81/134), of which 33.58% (45/134) had a clear molecular cause of deafness through genetic diagnosis. The proportion of deafness with no clues to the cause of deafness is about 40%, and this 40% of deafness may be related to environmental factors or to some currently unknown genetic factors. The percentage of deafness with a clear molecular cause through genetic screening for deafness is marked in green; the percentage of deafness with a molecular cause that is not yet known but is considered to be related to genetic factors is marked in blue; and the percentage of deafness without a clue to a cause through current research is marked in purple. GJB2 mutations are the most common cause of autosomal recessive deafness, and pathogenic mutations in two alleles can lead to the development of deafness. The proportion of deaf people carrying pathogenic mutations in one allele of GJB2 (monoallelic mutations) is significantly higher than in the normal population, so it is thought that monoallelic mutations in GJB2 are associated with deafness, but there may be additional factors involved in the development of deafness as well. In this region 17.16% carried the GJB2 double allele mutation and 13.43% carried the GJB2 single heterozygous mutation. Mutations in the SLC26A4 gene can cause enlargement of the vestibular canal, which is characterized by deafness and enlargement of the vestibular canal, and Pendred syndrome, which is characterized by enlargement of the vestibular canal, an inner ear structure, and goiter. It is well established that vestibular aqueduct enlargement is an autosomal recessive disorder, which is closely related to the SLC26A4 gene, and the detection rate of SLC26A4 gene mutation is about 97% in Chinese deaf people with vestibular aqueduct enlargement. CT examination of the temporal bone and genetic testing are powerful tools for the diagnosis of this disease. Patients carrying two alleles of the SLC26A4 gene generally definitely exhibit enlarged vestibular canals, and 30% of patients carrying a single allele of the SLC26A4 gene will exhibit enlarged vestibular canals. Deafness due to SLC26A4 mutations was found in nearly 15% of deaf patients in the region, and all of these patients had confirmed vestibular aqueduct enlargement by CT of the temporal bone. The proportion of the deaf population carrying one allele of SLC26A4 (single heterozygous mutation) was significantly higher than the normal population. In this region 6.71% carried the SLC26A4 monoheterozygous mutation. Mitochondrial A1555G mutation Mitochondrial A1555G mutation is a genetic factor with a clear pathogenic mechanism for deafness, and individuals carrying this mutation will become deaf after exposure to aminoglycosides (regardless of dose). The percentage of deafness caused by this mutation in the region is 0.76%. Individuals carrying the mitochondrial T1095C mutation also exhibit deafness after exposure to aminoglycosides, but the mechanism of deafness is poorly understood and is currently thought to be related to hereditary deafness. Family history of deafness is an indicator for initial identification of hereditary deafness. The cause of deafness was not clearly identified by genetic testing in deaf individuals in this region, but the percentage of individuals with a family history of deafness was 4.48%, and it is highly suspected that deafness in this group of deaf individuals is related to genetic factors. With the progress of medical science, the mystery of deafness will be gradually lifted and the percentage of deafness with unknown cause will be gradually reduced. With the clarification of the etiology, corresponding preventive and therapeutic measures will be improved, and in the future, premarital and prenatal genetic counseling and guidance can be requested for deaf people who have children with normal hearing in the next generation and whose molecular etiology is clear, and deaf people are expected to be free from generations of deafness.