It is important to identify foreign gene integration in genomose before transferring fertilized eggs to receptors in order to increase efficiency of producing transgenic animals.In this paper,PCR method was used to identify transgenic embryos to screen foreign genes integrating and no integating embryos.The construction that mice whey acidic protein (WAP) gene 2 6 kb promoter directed human granulocyte colony stimulating factor(G CSF) gene was used to microinject fertilized eggs of mice.In order to decrease the mistakes caused by PCR in screening transgenic embryo,two part of homologous recombinant fragments were constructed and used for co microinjection in to fertilized eggs of mice.PCR amplification fragment went beyond this homologous recombinant area.If foreign gene could be integrated to genomose,and two fragments of co microinjection could create homologous recombinant in embryos,the fragment of PCR amplification in embryos could be produced during embryo development.The results showed that specific fragments of PCR amplification could be obtained in different embryo developments and foreign genes integrated to genomoes cell stages 1,2 and 8 were 11 1%,55 5% and 44 4%,resprectively.Compared with other methods to screen transgenic embryo,this method might provide us a way to screen transgenic eggs efficiently when we use embryo section technique in farm animals.