【Objective】 To investigate the present situation of child's bone mineral density(BMD) in north china, and the relationship between child's BMD with ages, gender and seasons. 【Methods】 Analyzed the BMD and whose relationship with ages, gender and seasons of 5 971 normal children who came to our health center for body check in 2008-2009. 【Results】 The distribution of child's BMD normal and increased with the actual month. The relationship was linear and the difference was significant(P <0.001). BMD in different ages had significant difference. The relationship between BMD and gender was not significant before puberty(P>0.05). Only in adolescent ages BMD of girls was higher than boys and the difference was high significant(P<0.000 1). Child's BMD's Z-score had not significant difference in different seasons except of school age children.BMD's Z-score of infancy was lower in autumn than winter, and the difference was significant(P＜0.05). Child's BMD's Z-score of school ages was lower in summer than winter, and the difference was significant(P＜0.05). 【Conclusions】 Child's BMD of north china is increased with the actual month and correlate with gander and ages. Childs in adolescent should pay attention to take calcium and vitamin D. Child in summer and autumn should take appropriate amount vitamin D according to sunshine time.