Objective ：To measure the content of 25-(OH)D3(25-hydroxylase catalytic system generated ossification diol) in the blood serum of the children of different ages, and to probe into the relativity of 25-(OH)D3 with BAKP(bone alkaline phosphatase) and trace elements.Methods： Totally 382 cases of children were chosen, who took routine physical examination in the health care center of our hospital, as the research object.Divide the children into 5 groups according to their different ages:≤1，＞1～3，＞3～5，＞5～7 and ＞7～12. Detect the concentration of serum 25-(OH)D3, the serum BAKP and some trace elements, such as the Cu,Zn,Fe and Mg by using enzyme-linked immune testing method.Results： Children of all ages were obviously in lack of 25-(OH)D3.By using the Pearson correlation analysis, it was shown that the relativity between Zn and BAKP,Cu，between Fe and BAKP,Cu,Zn，between Mg and Cu,Z,Fe was very obvious(P<0.05).There was relativity between 25-(OH)D3 and BAKP(P<0.05).But there was no obvious relativity between 25-(OH)D3 and trace elements such as Cu,Zn,Fe and Mg(P>0.05).Conclusion： Children of 0～12 years old have different degree of 25-(OH)D3 deficiency, which is especially serious in the children of 0～3 years old.The relativity analysis shows that there is connection between 25-(OH)D3 and BAKP, but there is no connection between 25-(OH)D3 and such trace elements as Cu,Zn,Fe and Mg.Taking Zn and Fe can help improve the BAKP content,which is very beneficial to children′s health.