Objective: ITo study the changes of serum IL-10 levels in children with recurrent upper respiratory tract infections after vitamin D supplementation. Methods: 52 children with recurrent upper respiratory tract infections were randomly divided into 2 groups. The treatment group received conventional treatment combined with vitamin D supplementation. The control group received conventional treatment combined with placebo supplementation. All child patients were followed up for 12 months. The changes in serum 25-hydroxyvitamin D levels and serum IL-10 levels were examined before and after treatment. Results: Compared with the control group, serum IL-10 levels and 25-hydroxyvitamin D levels were significantly increased in the experimental group, and the number of respiratory infections was significantly decreased. During the one year follow-up, the serum 25-hydroxyvitamin D levels in the experimental group were positively correlated with the serum IL-10 levels. Discussion: Vitamin D supplementation helps to reduce the number of recurrent upper respiratory infections, which may be associated with increased IL-10 production.