Abstract: Objective This study was to evaluate the serum vitamin A level among under-three children in Guangzhou.Methods A total of 2792 children aged 6-30 months who received physical examination in children's health clinic during Nov 2018 to Apr 2019 were selected as subjects. Serum vitamin A levels were measured by electrochemical method using LK3000 V.Results The mean serum vitamin A levels was 0. 63 ± 0. 20 μmol/L. Serum vitamin A in children aged 6 months (0. 62 ± 0. 20 μmol/L) and in children age 12 months (0. 63 ± 0. 20 μmol/L) were lower than that in children aged 24 months (0. 66 ± 0. 21 μmol/L),which showed significant differences (F = 4. 117,P= 0. 006). The overall prevalence of vitamin A deficiency was 33. 1%. The highest prevalence of vitamin A deficiency was found in the 6 months age group (36. 2%). The prevalence of vitamin A deficiency were decreased with children's age (χ²= 4. 564,P= 0. 033). The prevalence of vitamin A deficiency had a increased trend with children's BMI,but there was no significant difference among different groups.Conclusions The prevalence of vitamin A deficiency is high among children under 3 years in Guangzhou,which is negatively correlated with children's age. More attention should be payed to vitamin A deficiency,especially in low age group.