Abstract: Objective To explorer the clinical significance of early application of synbiotics in high allergy risk infants and the effect on the percentages of TH9 cells and the expression level of IL-9 in peripheral blood.Methods 80 neonates with a family background of high allergy risk were randomly divided into the synbiotics intervention group (40 cases) and the control group (40 cases). The incidence of allergic diseases in the two groups within 6 months after birth was observed. The percentages of TH9 cells were detected by flow cytology and the expression level of il-9 in the serum were detected by ELISA.Results The incidence of allergy symptoms in the synbiosis intervention group was significantly lower than that in the control group, and the proportion of TH9 cells in the synbiotics intervention group was decreased (P<0.05), and the expression level of il-9 was lower (P<0.05).Conclusion Early application of synbiotics may reduce the occurrence and development of allergic diseases in children with high sensitivity risk to some extent, and is a safe and effective early intervention method, which maybe related to tht function of TH9 cells and IL-9.