The search for the cause of disease is the ultimate goal of medicine and a prerequisite for clinical diagnosis, treatment and prevention. With the continuous research on the molecular etiology of deafness and the advancement of genetic testing technology, especially the emergence of second-generation sequencing technology, deafness genetic testing has been able to move from laboratory to clinical application and from screening of individual loci to genetic diagnosis. What is deafness genetic diagnosis? A medical diagnosis is made by detecting changes in the structure or expression levels of genetic material in a patient’s body using molecular biology techniques, and is called genetic diagnosis (also called molecular diagnosis). Genetic diagnosis of deafness is simply the use of genetic testing technology to detect some or all of the known deafness genes in order to identify the disease-causing genetic mutations in patients and to make a medical diagnosis at the genetic level. Genetic deafness diagnosis is the key to the prevention and intervention of hereditary deafness by identifying the molecular cause of deafness and finding the causative gene mutation. Why is deafness genetic diagnosis necessary? There are two main points: 1. It is well known that most patients with hereditary deafness have sensorineural deafness with a very similar phenotype, and it is impossible to make a diagnosis of the cause of deafness based on clinical manifestations and conventional examinations (including physical examination, audiological tests, imaging tests, etc.), so only through genetic testing can an accurate diagnosis of the cause of deafness be made. 2. Therefore, only through genetic diagnosis, the molecular cause of hereditary deafness can be clearly identified, so that we can effectively carry out interventions such as marriage guidance and prenatal diagnosis to reduce the birth rate of deaf children. We often refer to primary and secondary prevention of deafness. From this perspective, genetic diagnosis is a prerequisite to address the root cause of hereditary deafness prevention and intervention. What are the genetic diagnosis techniques for deafness? The search for more efficient, accurate and economical genetic diagnosis techniques has been an important task in medical genetics. In the 21st century, molecular biology technology is changing rapidly, and genetic testing technology has been in a state of rapid iteration. Therefore, there is no accepted and fixed genetic diagnosis model for deafness at home and abroad, and the most common genetic test for deafness is Sanger sequencing (Figure 1), which is also the gold standard for clinical molecular diagnosis. Sanger sequencing (one-generation sequencing) is commonly used at home and abroad for deafness genetic testing of the three more common deafness genes (GJB2, SLC26A4, MT-RNR1), and thus its testing efficiency is low and costly, making it difficult to cope with genetic diagnosis of deafness, a disease with high genetic heterogeneity. Other genetic detection methods such as enzyme digestion, hybridization, and Taqman probes target mutation hotspots, but are usually only applicable to screening for certain specific loci. Recent advances in microarray microarrays have greatly improved throughput and reduced the cost of detection, but they are only suitable for hotspot screening, not genetic diagnosis.