Objective To investigate vitamin D level in children with cholestatic liver disease， and to provide a theoretical basis for vitamin D supplementation therapy in children with this disease. Methods A total of 116 children with cholestatic liver disease who attended Department of Traditional Chinese Medicine， Beijing Children’s Hospital， Capital Medical University， for the first time from January 2022 to January 2024 were enrolled and divided into groups for comparison based on sex， age， vitamin D supplementation dose， course of the disease， and etiology. The data on the serum level of 25-hydroxyvitamin D （25-OH-D） and related biochemical parameters were collected to assess the correlation between vitamin D level and biochemical parameters. The chi-square test or the Fisher’s exact test was used for comparison of categorical data between groups， and the Spearman rank correlation test was used for correlation analysis. Results Among the 116 children， 76 （65.5%） had vitamin D deficiency or insufficiency. The children with vitamin D deficiency or insufficiency accounted for 65.7% （46/70） among boys and 65.2% （30/46） among girls， with no significant difference between boys and girls （χ²=0.003， P=0.956）. The children with vitamin D deficiency or insufficiency accounted for 83.3% （25/30） among the children who had never received vitamin D supplementation， 58.7% （27/46） among the children with a daily supplementation dose of 500 IU， 64.3% （18/28） among the children with a daily supplementation dose of 700 IU， and 50.0% （6/12） among the children with a daily supplementation dose of>700 IU， and there was no significant difference between these groups （χ²=6.460， P=0.091）. Comparison between the groups with different etiologies showed that the children with vitamin D deficiency or insufficiency accounted for 57.7% （15/26） in the infectious disease group， 66.7% （10/15） in the inherited metabolic disease group， 66.7% （6/9） in the drug-induced liver injury group， 100.0% （8/8） in the group with abnormal structure of the biliary system， and 63.8% （37/58） in the group with unknown etiology， and there was no significant difference between these groups （χ²=5.304， P=0.252）. Comparison between the groups with different courses of the disease showed that the children with vitamin D deficiency or insufficiency accounted for 78.4% （29/37） in the<1 month group， 54.3% （25/46） in the 1‍ — ‍3 months group， 53.3% （8/15） in the 3‍ — ‍6 months group， and 77.8% （14/18） in the>6 months group， with no significant difference between these groups （χ²=7.432， P=0.059）. Comparison between different age groups showed that compared with the infant group， the children group had a significantly higher proportion of children with vitamin D deficiency or insufficiency （χ²=9.504， P=0.018）. The correlation analysis showed that serum aspartate aminotransferase and alanine aminotransferase had no significant correlation with 25-OH-D （P>0.05）； serum alkaline phosphatase （ALP） （r=-0.286， P=0.002）， gamma-glutamyl transpeptidase （GGT） （r=-0.248， P=0.007）， total bilirubin （TBil） （r=-0.353， P<0.001）， direct bilirubin （DBil） （r=-0.299， P=0.001）， and total bile acid （r=-0.236， P=0.011） were negatively correlated with 25-OH-D， while serum calcium （r=0.263， P=0.004） and phosphorus （r=0.385， P<0.001） were positively correlated with 25-OH-D. Conclusion Most children with cholestatic liver disease have vitamin D deficiency or insufficiency， and the increase in serum ALP， GGT， TBil， DBil or total bile acid and the reduction in calcium or phosphorus may suggest vitamin D deficiency or insufficiency.