Abstract: Through isoenzyme electrophoresis,microcytotoxity test and morphological analysis, the genetic characters and morphological features of 40 KM mice and 30 wild mice （Mus musculus castaneus） from Yunnan province of China were investigated, and compared with the wild mouse（Mus musculus domesticus） from western Europe. The results indicated： KM mouse was similar to M.m. domesticus in genetic profile. Both were identical in the shape of the zygomatic plate. Though KM mouse and Yunnan wild mouse contain Thy-1^a and Es-2^C which were lacking in M. m. domesticus, the genetic distance between KM mouse and M. m. domesticus was 0.2631，while it was 0.6165 between KM mouse and Yunnan wild mouse.The results suggested that KM mouse was originated from western Europe wild mouse （M. m. domesticus） and was genetically contaminated by M. m. castaneus after introduced into Yunnan province.

Key words: KM mouse, Mus musculus, Genetic profile, Zygomatic plate