Objective To investigate the relationship between age, gender, calcium supplementation during pregnancy, early symptoms of rickets and Z value of bone mineral density, and to provide evidence and recommendations for better prevention of rickets and low bone density in children. Methods Two thousand five hundred and four cases of infants aged 0-3 years old in the Qinhuai District Maternal and Child Health Hospital of Nanjing were tested with quantitative ultrasound bone density. The detection rate of bone mineral density was analyzed and age, sex, calcium supplementation during pregnancy and early stage of rickets. The relationship between symptoms. Results The bone mineral density Z value of girls aged 0-3 was lower than that of boys (P<0.001). In the 0-3 months, 3-6 mohth, 6 months-1 year groups, the incidence of under-bone density was significantly higher in girls than in boys (P<0.001). There was no significant difference in the detection rate of bone mineral density between boys and girls in the 1-3 years group (P>0.05). In the 3-6 months, the detection rate of infant bone mineral density was the highest, reaching 83.5%. The detection rate of girls with insufficient bone mineral density accounted for 51.0% of the total case of this age. There was a statistically significant difference in the detection rate of early symptoms and insufficient bone mineral density (P<0.001). There was no significant difference in the detection rate of calcium supplementation and bone mineral density during pregnancy (P>0.05). Conclusion It is necessary to regularly monitor the bone mineral density of infants and children, and pay attention to the bone mineral density of children within 1 year old, especially to girls.