Abstract: Objective In this study, spiral CT is applied in the measurement of crown facial prominences among people in Hohhot Mongolian school, from which we get the mean and the standard deviation of normal occlusal crown facial prominence. At the same time, the differences of the crown facial prominences can be determined through the comparative study between men and women. Methods 60 students with normal occlusion are selected in Hohhot Mongolian school, among which males and females are each half and age from 16 to 22. The upper and lower jaws of the selected samples are scanned by the GE64 -slice spiral CT machine, and data was analyzed by the Aw 4.4 resetting working station and 3D figures were reset with software to measure the crown facial prominence. Results U1、U 2、U 3、U 5、U 6、U 7、 L1 and L2 are statistically meaningful among people between males and females. Conclusion In orthodontic treatment , correctional quantity should be different between for Mongolian males and females .

Key words: Normal occlusion, Mogulation, Crown facial prominence, Spiral CT