Abstract: Objective : To assesse the applicability of Haavikko method in estimating the dental age of Nanjing children. Methods : A total of 629 dental panoramic radiographs(392 boys and 237 girls) of children in Nanjing were collected for the study on the basis of predetermined inclusion and exclusion criteria .All permanent mandibular teeth on the left side of the radiograph(except for the third molars) were assessed ,and the stages of development of these teeth were recorded according to Haavikko method .Paired t-test was performed between the chronological age and dental age which was scored by Haavikko method .A single-factor model was used to show the relationship between chronological age and dental age of Nanjing children. Result: A statistically significant difference was found between chronological age and dental age (P<0.01). Dental age scored by Haavikko method showed an underestimate of 0.6 years and 1.0 years in males and females. We set up the mathematical model between dental age and chronological age, then got the curve-fitting equation. Conclusions: The curve-fitting equation can be used to assess chronological age of Nanjing children, cause it shows No statistically significant difference between natural and dental age by using the equation.