Objective: To investigate the current status of fat-soluble vitamin supplementation in infants and young children in Huai’an, China the impact of different supplementation doses on their serum levels, and the nutritional status of fat-soluble vitamins in different age groups. Methods: Full-term infants aged 0-3 years who underwent health examinations at the Department of Child Health Care, Huai’an Maternal and Child Health Care Hospital from November 2017 to March 2018 were included. A self-designed questionnaire was used to investigate the supplementation of vitamins A and D preparations in infants, and high-performance liquid chromatography-mass spectrometry (HPLC/MS/ MS) was applied to detect serum levels of fat-soluble vitamins A, D, and E. Results: 1. Supplementation of vitamins A, D, and E preparations in infants within the month before the survey: 35.7% (75/210) of infants did not receive vitamin A supplementation, 57.6% (121/210) received intermittent supplementation, and 6.7% (14/210) received daily supplementation; 25.7% (54/210) of infants did not receive vitamin D supplementation, 29.5% (62/210) received intermittent supplementation, and 44.8% (94/210) received daily supplementation; none of the infants received vitamin E supplementation. 2. Serum vitamin A levels in infants who did not receive vitamin A supplementation within the past month were (1.04±0.30) μmol/L, those who received intermittent supplementation were (1.01 ± 0.28) μmol/L, and those who received daily supplementation were (1.00 ± 0.39) μmol/L (all p > 0.05); serum vitamin D levels in infants who did not receive vitamin D supplementation within the past month were (71.33 ± 23.92) nmol/L, those who received intermittent supplementation were (75.40 ± 20.52) nmol/L, and those who received daily supplementation were (81.43 ± 19.29) nmol/L, with the daily supplementation group showing higher levels than the non-supplementation group (p < 0. 05). 3. Serum vitamin A levels in infants were (1.02 ± 0.29) μmol/L, with 39.5% being normal, 55.9% marginally deficient, and 8.6% clinically deficient; serum vitamin D levels were (77.05 ± 21.25) nmol/L, with 90.5% being normal and 9.5% deficient; serum vitamin E levels were 10.24 ± 2.79 mg/L, with 98.6% being normal and 1.4% deficient. 4. Serum vitamin A levels in infants aged < 1 year were (0.89 ± 0.22) μmol/L, lower than those in children aged 1–3 years (p < 0.05); clinical deficiency of serum vitamin A in infants aged < 1 year was 13.7%, and marginal deficiency was 68.4 %, both higher than those in children aged 1–3 years (2.2% and 31.2%, respectively); normal serum vitamin A levels in infants aged < 1 year were 17.9%, lower than those in children aged 1–3 years (66.7%); differences between age groups were statistically significant (all p < 0.05). There were no statistically significant differences in serum vitamin D and E levels and their deficiency rates different age groups of infants (all p > 0.05). Conclusion: The daily supplementation of vitamins A and D preparations, especially vitamin A, in healthy infants in Huai’an, China during winter remains unsatisfactory; vitamin A deficiency is severe in healthy infants, especially infants, and the nutritional status of vitamin D still needs improvement, while vitamin E deficiency is rare. Pediatric workers should emphasize the importance of vitamin AD supplementation, especially vitamin A supplementation, in infants through publicity and education, and continuously improve the nutritional status of vitamins AD in infants.