Objective To study the effects of compound microecological preparation on the immune function of the intestinal mucosa of mice. Methods BALB/ C mice at 28 days of age were selected for use in this study, and composite microecological preparations of high, medium, and low doses (2. 5, 5 and 10 g / kg body weight) were given by gavage. Blood and jejunum tissue were sampled on the 14th and 28th days, and the immune organ index was measured. The blood lysozyme content was detected by turbidimetry, and the jejunum mucosa SIgA and immune cytokine (IL-4, IL-10 and IFN- γ) contents of mice were detected by ELISA. The expression of immunocytokine mRNA in the jejunum mucosa was detected by fluorescence quantitative PCR. Results (1) The different compound microecological preparation doses increased the SIgA and immune cytokine contents and enhanced the expression of immune cytokine mRNA in the intestinal mucosa of mice. On the 14th day, the contents of IL-4, IL-10 and IFN-γ; the expression of IL-4, IL-10 and IFN-γ mRNA; and the content of SIgA were significantly higher in the treated groups than the control group (P < 0. 01). On the 28th day, the content of IL-4 in the jejunal mucosa of the low-dose and medium-dose groups was significantly increased (P< 0.01). In the middle-dose group, IL-10 and IFN-γ protein and mRNA levels and SIgA protein levels were significantly higher than those in the control group ( P< 0.01). In the middle-dose and high-dose groups, IL-4, IL-10, and IFN-γ mRNA expression was significantly higher than that in the control group ( P< 0.05 or P< 0.01). There was no significant difference in the expression of IL-4 and IL-10 mRNA between the low-dose and control groups (P> 0.05). (2)On the 14th day, the immune organ index of the medium dose group was significantly higher than that of the control group (P< 0.05). (3)On the 28th day, compared with the control group, each experimental group’ s immune organ index was significantly increased (P< 0.05). The lysozyme content of each experimental group was significantly higher than that of the control group (P< 0.05). Conclusions Compound microecological preparation promoted the growth and increased the immune organ index, lysozyme content, and intestinal mucosal immune function of mice, consequently reducing the incidence of intestinal infectious diseases.