Objective To analyze vitamin D nutritional status among 25 295 children in Guangzhou area and investigate its correlation with age and season. Methods The serum samples of healthy children from Guangzhou Women and Children's Medical Center in 2012 were tested.Serum 25-hydroxyvitamin D[25-(OH)D] concentration was determined by ELISA kits.Serum Vitamin D status was classified into 3 groups according to its serum 25-(OH)D levels,severe deficiency(<12.5 nmol/L),deficiency(12.5~37.5 nmol/L) and insufficiency(37.5~50.0 nmol/L).Statistical analysis were done with SPSS 17.0 software. Results Totally,25 295 children samples were detected in 2012.The average serum 25-(OH)D concentration was 72.41 nmol/L.No significant correlation was found between the serum 25-(OH)D concentration and gender.Severe deficiency case was not found.The vitamin D concentration <50 nmol/L was 13.22%.The 25-(OH)D concentration decreased with age.The lowest concentration of vitamin D was found in Jan 2012.Then it increased gradually from Jan.to July,peaking in Aug.and Sep.and slow declined.Meanwhile,he vitamin D deficiency and insufficiency rate was peaking in Jan.and lowest in Sep..Conclusion The vitamin D concentration is lower in autumn and winter.The vitamin D nutritional status of children over 3 years old in Guangzhou is deficiency.