Objective To explore the clinical and gene mutation characteristics of KCNT1 gene mutation associated epilepsy in infancy with migrating focal seizure. Methods The clinical data of KCNT 1 gene mutation associated epilepsy in infancy with migrating focal seizure in 3 children were retrospectively analyzed, and the related literature was reviewed. Results In 2 girls the age at onset was 3 months and at 6 months respectively. In 1 boy the age at onset was 2 months. All the 3 cases were onset with convulsions and diagnosed as new missense mutations of KCNT 1 gene by genetic test, which were respectively c. 862 G>A(p.Gly 288 Ser), c. 2813 A>G (p.Tyr 938 Cys), and c. 1283 G>A(p.Arg 428 Gln). The head magnetic resonance imaging of 2 cases was normal, while 1 case showed delayed myelination and thin knee of corpus callosum. VideoEEG showed focal status epilepticus in 2 cases, of which 1 case had hypsarrhythmia. All the 3 cases were treated with various antiepileptic drugs, but seizures failed to be effectively controlled, and cases appeared motor retardation and even regression. Conclusion KCNT 1 may be the main pathogenic gene of EIMFS,and leads to early onset of epilepsy often accompanied by developmental retardation, poor response to multi-antiepileptic drugs and poor prognosis.