To study the changes of inorganic and organic substance around cementum-dentin junction in the tissues of human natural tooth, the method of electron probe microanalysis was used in this research project. Determinations of weight percentage (wt%) were made for Ca, P and S elements around cementum-dentin junction. The results showed that the changes in quantities of Ca, P and S elements around cementum-dentin junction were not significant(P > 0.1). These suggest that the quantities of inorganic and organic substance have not obviously varied with the anatomic structure of natural tooth.