Abstract: Objective To understand the knowledge,attitude and behavior about fragile X syndrome among the parents of mentally retarded students,so as to provide basic data for further screening population athigh risk.Methods 822 parents with children from special education schools in Beijing and Tianjin were investigated through questionnaire survey.Results More than 95% parents didn' theard of fragile X syndrome,with little knowledge about the cause and clinical feature.88.2% parents were willing to learn the related information,such as its cause,treatment/rehabilitative methods.And about 85% parents would like to take their children to examine the disease and follow a genetic consultation.Conclusion The parents with mentally retarded students knew little about the fragile X syndrome,but whose acceptability of screening was high.