Bacterial lac operon can regulate gene expression in mammalian.Modified lac operon alter the inducibility and affinity binding to lac operator,which will be better to adapt higher animals' internal environment.Galactosidase has a positive regulation effect on the lac operon system.Lac operon regulate galactosidase inducible expression can improve transgenic animals' ability of making full use of galactoside.Following from the structure and function of lac operon,the gene regulation properties,combined with galactosidase's physiological functions and applied in transgenic animals are reviewed.Analysis prospect of the lac operon mediated galactosidase applied in transgenic animals.