There is a role for genetic testing for some specific types of diabetes to help clarify the diagnosis. Genetic diagnosis can be done in patients suspected of having diabetes with a single gene mutation. Single gene defects in pancreatic β-cell function such as glucokinase gene mutations lead to adult onset diabetes in adolescents, and single gene defects in insulin action such as insulin receptor gene mutations lead to type A insulin resistance, short goblin look syndrome, and so on. Single gene defects in insulin action, such as mutations in the insulin receptor gene, lead to type A insulin resistance and dwarf goblin look syndrome. Special types of diabetes caused by genetic defects in pancreatic β-cell function, such as mitochondrial mutation diabetes mellitus, are the most common type of single-gene mutation diabetes mellitus, accounting for 0.6% of all adult diabetes mellitus in China. When special type of diabetes mellitus is suspected, genetic examination or chromosome examination can be done according to the clinical characteristics of the patient, in order to clarify the diagnosis and treatment as early as possible, and follow the doctor’s instructions to actively treat.