This paper presents the results of study on genetic variants of 4 KM subcolonies maintained in Beijing, Shanghai, Changchun and compares it with that of one NIH colony introduced from U.S.A. by methods of eletro-phoresis and mandible analysis, The results revealed that: (1) There are significant differences between KM and Swiss derivative colony NIH on alle-lic constitutions of Es-3, Es-10, Glo-1, Gpt-l, Got-2, and Mpi-1 loci and mandible shape. Genetic distance between NIH and KM subcolonies is 0.131, 0.011, which is a proof that KM mice is non-Swiss derivative subspecies. (2) The allelic constitutions of KM subcolonies is same and genetic distance is 0.008, 0.027 positively related with the time of colony closed. (3 ) The unique position of S:KM mouse was shown in phylogenetic diagram of 4 KM subcolonies from both biochemical and morphological data,which prompts that some variants existed in KM subcolonies may influence the repro-ductivity of experiment.