Abstract: Objective Through the analysis of the influencing factors of serum 25(OH) D₃ level among 0-3-year-old infants to provide scientific basis for effectively controlling and reducing the occurrence of vitamin D deficiency in infants.Methods From July 2017 to December 2018,1407 0-3-year-old infants in the growth and development clinic of children's health care department of Luohu District Maternal and child health care hospital were measured with 25(OH) D₃ quantitative method and questionnaire.Results The detection rate of 25(OH) D₃ deficiency was 14.1%. There were statistically significant differences in the levels of 25(OH) D₃ between 0-3 years old infants and young children of different ages and different gestational weeks(P<0.05). Linear regression analysis showed that season of pregnancy and father's education level were the influencing factors of children's 25(OH) D₃ level.Multivariate logistic regression analysis showed that the gestational age and season of pregnancy were the influencing factors of vitamin D deficiency(P<0.05).Conclusion The nutritional status of vitamin D in infants aged 0-3 in Luohu District is relatively good,but vitamin D supplementation for children within 3 months of age should be further strengthened. Season of pregnancy and father's education level are the influencing factors of children's 25(OH) D₃ level. The protective factors of vitamin D deficiency were gestational age≥37 weeks,pregnancy in summer and autumn(P<0.05).