Objective　To explore the clinical characteristics of Coffin-Lowry syndrome. Method　The clinical data and genetic testing of Coffin-Lowry syndrome in a child were retrospectively analyzed, and pertinent literature was reviewed. Results　A boy aged 4 years and 3 months visited for mental retardation. The child have special face such as microcephaly, prominent forehead, hypertelorism, downward sloping palpebral fissures, a flat nasal bridge, a wide mouth with full lips and enamel dysplasia, large ears,  and puffy tapered fingers. Genomic sequencing and bioinformatics analysis showed that exon 5 of RPS6KA3 gene has a hemizygous mutant c.340C>T (cytosine > thymine) which caused the changes in amino acid p.Arg114Trp (arginine > tryptophan), and the diagnosis of Coffin-Lowry syndrome was confirmed. Conclusion　Children with Coffin-Lowry syndrome have mental retardation and special facial features, and gene detection helps early diagnosis.