Abstract: Specific pathogen free KM mice were obtained from Cesarean section. Random mating system （rotational mating） was established to produce and maintain the mice in the barrier system. The growth rate and reproductive performance and genetic profiles were measured and detected in the fifth and tenth generation of the random mating groups. The results were compared with those of the chance mating group,and was verified that the random system mating method is an important measure for the maintenance of out bred colonies.