OBJECTIVE:Mannan-binding lectin (MBL) is a C-type serum lectin that plays a central role in the innate immune response. At present there is no a reference range of serum MBL levels for children in China. This study investigated serum MBL levels in preschool children from Shenzhen. METHODS: A total of 118 children (62 boys and 56 girls) at ages of 3-6 years and sampled randomly from three kindergartens of Shenzhen were enrolled in this study. Serum MBL concentrations were determined using enzyme-linked immunosorbent assay. RESULTS: The mean serum MBL concentration in these children was 779.07±268.98 ng/mL. There were no significant differences in the value of serum MBL between boys and girls (783.89±252.30 ng/mL vs 773.65±288.29 ng/mL) (P>0.05). Sixteen children (13.6%) had MBL concentrations less than 500 ng/mL (the low limited value used abroad), including 14 cases with 50-500 ng/mL and 2 cases with less than 50 ng/mL. CONCLUSIONS: This study provides a reference range of serum MBL concentration for preschool children. MBL may be a useful marker for the prevention of infection in children.