Objective : To investigate the correlation between vitamin D levels and the risk of early childhood caries (ECC), and to provide a reference for the primary prevention of ECC in children. Methods : A total of 389 children aged 6 months to 48 months were enrolled in this study. Data of feeding patterns and oral health behaviors were collected, and decayed-missing-filled teeth (dmft) were recorded. The children were divided into an ECC group (dmft > 0, n= 146) and a caries-free group (dmft=0, n=243). Peripheral blood of fingertips was collected to detect the active form of vitamin D--25(OH)D in vivo, and the cariogenic activity of dental plaque was analyzed with the Cariostat test. Logistic regression analysis was carried out to analyze the correlation among caries related factors such as 25(OH)D levels and caries risk in patients with ECC. Results: There was no significant difference in the prevalence of dental caries among 25(OH)D deficiency, insufficiency and normal children (χ2=2.320, P=0.313). There was no correlation between dmft and 25(OH)D levels (dmft=1-3, r < 0.001, P > 0.05; dmft > 3, r= 0.009, P > 0.05). The risk factors for ECC were age (OR=1.082, 95% CI: 1.045-1.121, P < 0.001), breastfeeding within 6 months after birth (OR=2.789, 95% CI: 1.581-4.921, P < 0.001), nighttime milk consumption or sleeping with a nipple (OR=4.187, 95% CI: 1.938-9.048, P < 0.001), and a high Cariostat value of 1.5-3.0 (OR=4.173, 95% CI: 2.014-8.646, P < 0.001). Conclusion There was no correlation between 25(OH)D level and caries in children aged 6-48 months. The risk factors for ECC are age, breastfeeding before 6 months old, nighttime milk consumption or sleeping with a nipple and high cariogenic activity (Cariostat value of 1.5-3.0). It is necessary to establish good feeding habits and oral hygiene habits for children while promoting breastfeeding.