Background：Vitamin D insufficiency and deficiency in childhood are common, and they are closely related to bone development. However, the status and influential factors of vitamin D during different ages are not clear. This study aimed to survey vitamin D status in children aged 0 to 6 years and explore its influential factors. Materials and methods: A total of 6953 children were recruited in Wuxi City of East China from January to December 2016. Enzyme-linked immunosorbent assay was used to determine the serum concentrations of 25-hydroxyvitamin D [25(OH)D]. Results: The median vitamin D level in the infancy group (0-1 years of age) was 69.40 nmol/L, which was higher than that in both the toddlerhood group (1-3 years of age; 62.30 nmol/L) and the preschool group (3-6 years of age; 50.85 nmol/L) (P < 0.001). In addition, the median vitamin D level was 71.70 nmol/L in summer, which was higher than that in spring (64.25 nmol/L), autumn (62.95 nmol/L) and winter (64.10 nmol/L; P < 0.001). However, no difference was observed between genders (P = 0.974). Furthermore, the prevalence of vitamin D deficiency (<50 nmol/L) was 48.1% in the preschool group (3-6 years of age), which was higher than the 21.2% vitamin D deficiency in the toddlerhood group (2-3 years of age) and the 17.9% vitamin D deficiency in the infancy group (0-1 years of age). Interestingly, a nonlinear association between 25(OH)D and air temperature was observed. Conclusions: A high prevalence of vitamin D deficiency was common in a Chinese population of children 0-6 years old, especially in the preschool-aged group. Season and air temperature were related to vitamin D status. Therefore, we suggest that the recommendation for vitamin D supplementation in the Chinese pediatric population should be revised to include older children and adolescents.