Objective To breed transgenic mice containing xylE gene and to screen homozygous transgenic mice. Methods Two founders(G 09 and G 031) of transgenic mice containing a %xylE% mutational target gene were selected for breeding. G 09 and G 031 were mated with nontransgenic ICR mice respectively and F 1 offsprings were produced. F 2 and F 3 offsprings were generated by inbreeding of the same litters of F 1 or F 2 respectively. Results Their offspring's phenotype had no detectable abnormal. Detection of line 31 indicated that the %xylE% target gene could stably transmit to the next generations. One homozygous male mouse of line 31 by PCR had been confirmed. Through mating the mouce to nontransgenic partners, all the 28 offsprings (four litters) were transgenic by PCR-Southern detection. Conclusions 1.Transgene could be stably transmitted to F 3. 2.One homozygous transgenic mouse was screened within 4 generations of line 31.;