This study was aimed to assess the protective effect of sodium selenite on the ileum mucosal immunologic injury induced by AFB1. One hundred eighty-one-day-old healthy male Avian broilers were divided into four groups of three replicates and 15 birds per replicate and fed with basal diet (control group), 0.3 mg/kg AFB1 (AFB1 group), 0.4 mg/kg Se (+Se group), and 0.3 mg/kg AFB1 + 0.4 mg/kg Se (AFB1 + Se group) respectively. The numbers of IgA(+) cells of ileum were determined by immunohistochemistry as well as the contents of sIgA, IgA, IgG, and IgM in the mucosa of ileum by ELISA. Compared with those in the control group, the numbers of IgA(+) cells as well as the sIgA, IgA, IgG, and IgM contents were decreased in the AFB1 group. However, compared with those in the AFB1 group, the numbers of IgA(+) cells as well as the sIgA, IgA, IgG, and IgM contents were increased in the AFB1 + Se group, and these data had no difference between AFB1 + Se group and control group. It was concluded that 0.3 mg/kg AFB1 could reduce the humoral immune function of the ileum mucosa, but 0.4 mg/kg supplemented dietary selenium could protect the mucosal humoral immune function from AFB1-induced impairment.