Abstract: Objective：To study the applicability of Demirjian’s method for age estimation in children of Nanjing．Methods： 644 panoramic radiographs(378 boys and 266 girls) which were collected from the stomatological Hospital of Jiangsu Province were involved in this study with chronological age from 3 to 16 years. Paired t-test was performed between the chronological age and the age determined by Demirjian’s method. Single-factor model was used to explore the relationships of the two kinds of age. Results：For the marked difference between the chronological age and determined age(P<0.01),Demirjian’s method was not suitable to the children in Nanjing. We set up the mathematical model between tooth maturity and natural age of children in Nanjing, then got the curve-fitting equation. For boys: Y=43.37*Sin(0.02579X-1.138)+30.6*SIN(0.04275X+0.9984)+3.019*SIN(0.08706X+1.649), and for girls: Y=55.93*SIN(0.04001X-1.642)+90.97*SIN(0.05389X+0.7095)+44.25*SIN(0.06254X+3.384).The Results of paired t-test between chronological age and predicted age from quadratic equation showed that there was no significant difference in boys and girls(P>0.05). Conclusions：Through the establishment of mathematical model between tooth maturity and natural age in this study, we can determine the natural age from 3 to 16 in Nanjing children more accurately by utilizing tooth maturity.