Abstract: Objective To introduce the rare autosomal dominant Costello Syndrome through literature review after diagnosing the 1st Chinese patient by direct sequencing of HRAS gene. Methods Total genomic DNA was extracted from peripheral blood leukocytes of the patient and her parents. The coding exons 2-5 of the HRAS gene were amplified by polymerase chain reaction (PCR) and sequenced directly. Results A common HRAS missense mutation, p.Gly12Ser, was identified in the patient，but not in the parents. Conclusion Patients with Costello syndrome manifest characteristic facial features, feeding difficulties and developmental delay/mental retardation etc. The diagnosis can be confirmed by mutation analysis of HRAS gene.