Abstract: By mating transgenic mice, transgenic mice model of high expression of foreign gene was screened. Making use of conventional way of breeding to mate 2(A♀,B♂)transgenic mice integrated Hepatitis B virus(HBV) gene, 2A(♀♂) and 2B(♀♂)transgenic homozygote mice, and 6 bi-heterozygote mice(4♀2♂) by mating A and B homozygote mice were taken. Blood serum of these transgenic mice and their off-springs’ were collected, and HBV DNA expressing in blood serum of transgenic mice was tested by polymerase chain reaction and ELISA (PCR-ELISA). The results were as follows: HBV DNA expression in the blood of bi-heterozygote mice was much more than that of homozygote and heterozygote mice. Breeding bi-heterzygote mice is likely to be a good way of high expression of foreign gene in transgenic animals.