The Homozygosity was studied by skin isografting in the segregating inbred strain of YuYi Hairless mice. There were no acute or chronic exclusions with YYHL mice after being observed for 100 days. All te grafts were taken permanently The results showed that the histocompatibility antigens are identical and the genes are isogenicity in the mutation mice inbred for 20 generations. The mice were comfroned to inbred strain.