Objective:To explore the clinical and genetic characteristics of a child with mental retardation, language and motor developmental delay and epilepsy.Methods:A Child who was admitted to the First Affiliated Hospital of Zhengzhou University in March 2020 for intermittent seizures for over two months was Selected as the study subject. Clinical data of the child was collected. Peripheral blood samples of the child and his parents were collected and subjected to high throughput sequencing. Candidate variants were verified by Sanger sequencing and bioinformatic analysis.Results:The clinical manifestations of the child have included mental retardation, language and motor developmental delay, and seizures. High-throughput sequencing revealed that he has harbored a hemizygous splice site variant (NM_032591.3: c.1030-1G>C) of the SLC9A7 gene, which was inherited from his mother and unreported previously. Conclusion:The hemizygous splice site variant (NM_032591.3: c. 1030-1G>C) of the SLC9A7 gene probably underlay the disease in this child. Above finding has provided a basis for clinical diagnosis and genetic counseling.