The clinical features and gene mutation characteristics of 2 children who suffered from Cornelia de Lange syndrome(CdLs)and were admitted to Affiliated Hospital of Zunyi Medical University in March 2019 were retrospectively analyzed.The 2 cases developed in infancy and presented with intractable epilepsy were accompanied with developmental retardation and special appearance.It was obvious that the 2 children had SMC1A gene mutations on X chromosome.Case 1 was frameshift mutations in the SMC1A gene at c. 2561dupA(p.K854fs), and case 2 was mutations in the SMC1A gene at c. 3441+ 1G>A(exon24)splicing mutation.These were heterozygous de novo mutations, and weren′t detected in their parents, which was not reported in literatures.In this study, 2 cases of CdLs were caused by SMC1A gene mutation, which enriched the human gene mutation database.CdLs should be considered in children with early-onset epilepsy, especially appearance and developmental retardation.Genetic testing is the most important diagnostic method.