Objective To understand present situation and change rule and influence factors of ultrasonic bone mineral density of the city children under the age of six, to provide reference data of normal population and the work direction for bone health care of children. Methods From June 2011 to December 2012, bone mineral density testing of healthy children in our hospital detected 7 064, including male 3 681, female 3 383.Using Israel Omnisense 7000P type of quantitative ultrasound bone density detector, in accordance with the standards for bone mineral density testing, the left tibia interrupt point for babies under 3 years old the radial 1/3 as the measurement point for the children aged ≥3, the ultrasonic speed (the speed of sound, SOS) value were measured.At the same time, application of self-made questionnaires, to parents of children collected with accurate records of children including the children's date of birth, family income, educational level of parents, parenting culture degree, family type, pregnant condition, feeding, vitamin D and calcium supplementation, the time for outdoor activities, there is no familial bone disease and other major diseases. Results The normal range of ultrasonic bone mineral density values of children below 6 years old in 1, 12, 24, 36, 48, 60 months old were:(2 877.23±214.44), (3 275.32±215.89), (3 459.66±195.60), (3 577.46±300.45), (3 605.55±288.53), (3 642.49±288.04)m/s, with the age increasing gradually increase.Within 3 years old the bone mineral density increased rapidly, especially infants.After the age of 3, bone mineral density increased slowly, there was a significant difference between different age groups (P<0.01).Among all age groups, the t test showed that differences between boys and girls had no statistical significance (P＞0.05).Multiple conditional Logistic regression analysis showed:mother late gestation supplement vitamin D, given daily oral vitamin D in children aged, active/passive movement, timely add animal food, outdoor activities are protective factors of bone mineral density in children. Conclusions The establishment of ultrasonic bone mineral density normal range values in children under the age of 6.Can provide clinical reference for the future of children's bone health Yidu city.