Objective To explore the clinical characteristics, diagnosis and treatment of early-onset epileptic encephalopathy caused by KCNT1 gene mutation. Methods The clinical data of an early-onset epileptic encephalopathy associated with KCNT 1 gene mutation in a child were retrospectively analyzed, and the related literature was reviewed. Results The female patient aged 2 years and 7 months had frequent seizures since the neonatal stage and the main manifestation was focal clonic seizures accompanied by developmental retardation. The electroencephalogram showed epileptic discharge. There were no obvious abnormalities in cranial imaging and genetic metabolism screening. Genetic testing showed a mutation of c.1041G>C (p.Glu 347 Asp) (NM_ 020822 . 2 ) in KCNT 1 gene. The seizures were relieved after treatment with oral quinidine. Conclusion KCNT1 gene mutation-related early-onset epileptic encephalopathy can be onset in the neonatal period with abnormal psychomotor development. Quinidine may be effective for the treatment.