【Objective】 To investigate the development and trend of pupillary distance among 6 to 15 years old children in Gansu Province. 【Method】 Pupillary distance samples of 8 164 children living in the 6 districts of Gansu province:Lanzhou,Zhouqu,Huinin,Baiyin,Jinning and Hezuo were measured using steel ruler and the results were analyzed and compared cross age and gender sections. 【Results】 Among 8 164 samples,6 to 15 years old boys' pupillary distance increased from 55.60mm to 61.49mm while girls' increases from 56.04mm to 60.24mm,i.e.pupillary distance increased as age increased.Pupillary distance and age showed positive associations (male:r=0.335,P<0.01;female:r=0.286,P<0.01).And the differences between different age group were significant.Other than 6 age groups,boys' pupillary distance was larger than girls.The gender difference of 6 to 10 year's age group was not significant,but between 11 to 15 years old age group there was significant difference.In Gansu province the pupillary distance of 6 to 15 years old children increased as their age increased.Both male and female pupillary distance showed rapid increase at the age of 9.But after reaching 13 years old,female pupillary distance stopped increase while male pupillary distance continued to grow after 15 years old.Male pupillary distance reached adolescent level at the age of 14 while female at 11. 【Conclusion】 The pupillary distance data of normal developed children is an import reference in diagnosing children's abnormal skull development.