Objective　To explore the clinical characteristics of neonatal-onset epileptic encephalopathy caused by KCNQ2 gene mutation. Method　The clinical data of 9 cases of neonatal-onset epileptic encephalopathy caused by KCNQ2 mutation were retrospective analyzed. Results　In 9 children (5 boys and 4 girls), median onset age was 2 days (0.5 hours to 8 days) and the median age was 10 months (1 month to 5 years) at the time of diagnosis. A total of nine heterozygous de novo KCNQ2 missense mutations were identified. They had common features such as tonic seizures or asymmetrical tonic seizures and a suppression-burst EEG pattern. Five cases were diagnosed of Ohtahara syndrome and four cases were diagnosed of unknown syndrome epileptic encephalopathy. After treatment with multiple drugs, 6 cases were seizure free. All of them had obvious motor and mental retardation. Conclusion　Epileptic encephalopathy caused by KCNQ2 mutation mainly occurs within one week after birth, and the prognosis is poor. Gene detection can confirm the diagnose.