Objective To explore the relationship between infant vitamin D level and ultrasonic bone mineral density and height development,and to discover the high risk factors of infants with vitamin D deficiency rickets,and provide the basis for the confirmed diagnosis of vitamin D deficiency rickets. Methods 337 cases of 9 months old infants born from in March 2010 to in April 2011 in our hospital and in routine register system management of the children's health section were selected.Weight and height were measured and recorded according to the indexes measuring method of growth and development and the questionnaire survey of feeding patterns was collected.5mL infant venous blood was collected in 9 months' medical examination,Serum 25-(OH) D was detected by ELISA,infant tibia SOS was measured by 7000P bone ultrasound intensity meter provided by the Sunlight Omnisense.Bone mineralization condition was showed and compared by Z value.The relationship between infant vitamin D level and ultrasonic bone mineral density and height development was analysed by the single factor variance analysis and independent sample t test. Results Different feeding methods,duration of breast feeding and the time for outdoor activities were compared,there were differences in the different groups of vitamin D level and ultrasonic bone mineral density in Z value (P<0.05).There was a significant difference in 25-(OH)D,ultrasonic bone mineral density Z value and height in the different groups(P<0.05). Conclusions Infant vitamin D nutritional status is closely related to bone mineral content.Reasonable amount of vitamin D is the future focus of child protection work.It was confirmed 25-(OH)D is the gold standard for the diagnosis of vitamin D deficiency rickets.The examination of infant serum 25-(OH)D of conditional units is suggested.