Objective To investigate the levels and deficiency of 25-hydroxy vitamin D[25-(OH)D] in children at 0~16 years old in Nanjing area. Method Serum levels of 25-(OH)D in 2 266 cases of children at 0~16 years old,detected by enzyme linked immunosorbent assay (ELISA) between April 2012 and March 2013,were statistically analyzed. Results 1) Among 1 204 cases of children in winter and spring,the serum level of 25-(OH)D was (55.1±19.58)nmol/L (male 778,female 426),there had no statistical difference between different gender groups.And there had statistical difference among group lower than 1 year old [(71.7±27.39)nmol/L],group 1~7 years old[(59.6±18.25)nmol/L] and group more than 7 years old[(46.9±14.97)nmol/L].2) Among 1 062 cases of children in summer and autumn,the serum level of[25-(OH)D] was (67.2±46.89) nmol/L ( male 670,female 392 ),there had no statistical difference between different gender groups.And there had statistical difference among group lower than 1 year old [(98.0±39.97)nmol/L],group 1~7 years old [(73.0±61.73)nmol/L] and group more than 7 years old [(55.8±16.75)nmol/L].3)There had statistical difference between different season groups (P<0.01). Conclusion The serum levels of 25-(OH)D of 0~16 years old are sub clinic deficiency except group lower than 1 year old in Summer and Autumn.And the serum levels of 25-(OH)D decrease gradually by the age of children increasing.