Abstract: 【Abstract】Objective To testify the Bolton index and the incidence of Bolton index disorder among three types of Angle class malocclusion in Urumqi area. Methods The orthodontic plaster models in Stomatology Department of No.5 Affiliated Hospital of Xinjiang Medical University from 2015.01 to 2018.01 were selected.Based on Angle malocclusion classification,120 males and 120 females were recruited and divided into three groups，80 casts in each group. Bolton index anterior and overall tooth ratio were measured and calculated for all models.According to the average normal Bolton index standard of Chinese, the incidence of Bolton index irregularity of the Urumqi area was obtained. Then calculate the Bolton index range of Urumqi area and compare with the normal value of the Chinese.Results The incidence of Bolton index anterior tooth ratio and overall tooth ratio discrepancy of malocclusion patients in Urumqi area were 57.08%、40.83%. Bolton index discrepancy of di fferent malocclusions has statistical difference (P＞0.05).And there was no difference of Bolton index discrepancy between sexes (P＞0.05).There was no difference between Bolton index in Urumqi area and Bolton index of Chinese normal occlusion (P＞0.05).If 1.5 mm Bolton tooth size discrepancy（TSD）was used, The incidence of anterior and total teeth discrepancy was 15.4%and 15 % ,seperately.There was significant difference in the incidence of total tooth size discrepancy among the three types of Angle malocclusion (P＜0.05).Conclusion The incidence of Bolton index disorder in Urumqi area is high,which should be a routine measure for the diagnosis and design of malocclusion patients.

Key words: Bolton index disorder, Tooth size discrepancy, Urumqi