Abstract: Objective To establish the database of teeth and dental arch by CT 3D-measurement on permanent normal occlusion of the youth in Harbin, and to provide practical basis for the clinical application. Methods The untreated normal occlusion of 50 Harbin youth aged 18-25 were evaluated by means of the spiral CT and AW4.2 workstation. Some diagnoses items were measured, and dentition indexes and linear correlation of normal occlusion were obtained. Results ①The width, angle, latero-length of the dental arch in men were significantly larger than those in women.② In normal occlusion, dental arch was generally symmetric, but there was asymmetry to a small degree. Right canine latero-length in men was larger, while left molar latero-length in women was larger. ③There was no marked sexual difference showed in tooth size. ④The sexual dimorphism was found in Bolton＇s index of anterior teeth group. ⑤The correlation analysis of inter-arch tooth size revealed that there were significant positive relationships between upper anterior teeth group and lower＇s and between upper overall teeth group and lower＇s, and additionally sexual differences were found in incisor teeth group and lateral teeth relationship. Conclusion ①The dental arch of men is wider than that of women.② Dental arch is not exactly symmetric, and superior sides were noticed in right canine part of men and left molar part of women. ③ When we estimate the lateral teeth size, appropriate references are upper incisor teeth for men and lower incisor teeth for women.