Objective: We aimed to investigate the relationship between vitamin D status and core symptoms and neuro-developmental levels in children with ASD with a multicenter survey.Methods: We enrolled 1321 ASD children and 1279 typically developing (TD) children aged 2-7 years from 13 cities in China. ASD symptoms were assessed with the Autism Behavior Checklist (ABC), Social Responsiveness Scale (SRS) and Childhood Autism Rating Scale (CARS), and neurodevelopmental levels were evaluated with the Children Neuropsychological and Behavior Scale-Revision 2016 (CNBS-R2016).Results: Children with ASD had lower serum 25(OH)D levels than TD children. Serum 25(OH)D levels were negatively associated with CARS and communication warning behavior of CNBS-R2016 scores, and were not associated with the development quotients of ASD children. ASD Children were grouped based on the quartiles for 25(OH)D levels in the controls, and children in the first to third quartiles had higher SRS social communi-cation and/or CARS and communication warning behavior of CNBS-R2016 scores than those in the fourth quartile.Conclusions: Serum 25(OH)D levels were primarily associated with core symptoms in children with ASD, and individuals with relatively lower 25(OH)D levels displayed worse autistic symptomatology. More research is needed to determine whether vitamin D supplements would be a useful treatment for ASD.