Sex identification of cow embryo in its early stage is very important.It is the premise of the possibility that the technology of seperating and transplanting cow embryo can bring about great economic efficacy. PCR technology is an accurate, speedy and sensitive method in sex identification of cow embryo.Usign the human sex differentiation relevant DNA sequences ZFY and ZFX,two primers are designed and a fragment is amplified from the male or female cow genomic DNA.Then the fragments are cloned into the vector pUC118 and are sequenced. It is found that the fragments from ZFY gene and ZFX gene have 88.2% homologous regions. Upon this，primers and probes can be designed to identify the cow sex sensitively by means of PCR.