Objective To breed and identify fragile X mental retardation 1(FMR1) gene knockout mice.Methods The FMR1 gene knockout mice were introduced and the genome DNA of tails of mice was extracted and identified by PCR,then male homozygote mice were attained and selected to mate with female heterozygote mice to acquire homozygote baby mice with gene knockout.Results The feeding and breeding were successful and more homozygote baby mice with gene knockout were attained.Conclusion Appropriate methods of feeding,breeding and identifying are the effective ways to acquire homozygote baby mice with FMR1 gene knockout.