Abstract: The disclosure discloses application of breast milk-derived Lactobacillus reuteri in regulating the maternal and infant immune function, belonging to the fields of microbiological technology and food science. The disclosure provides the effects of Lactobacillus reuteri Fn041 in enhancing the immunity of pregnant or lactating women and infants, i.e., enhancing the mucosal barrier, promoting the production of intestinal antibacterial peptides and IgA, promoting the development of the immune system of infants, preventing pathogen infection and reducing the incidence of allergic diseases.