Abstract: Abstract: Objective To investigate the upper airway of patients who were treated with Damon bracket and non-extraction technique and to observe the changes of morphology and structure of the upper airway before and after operation based on CBCT scan. Methods CBCT images of 14 patients with Damon bracket and non-extraction were collected. Then Dolphin was used to rebuild 3D image data. According to anatomical structure, upper airway can be divided into four sections: nasopharynx, velopharyngeal, tonguepharyngeal, laryngopharyngeal. Airway volumes, across-sectional area and height were measured . All the data were analyzed by SPSS software. Results After the orthodontic treatment, most of measures of upper airway increased except the volume of nasopharynx which decreased 134.85 mm3 (2.2%，P=0.796）compared with pre-treatment. The volume of upper airway increased 2013.46 mm3 (9.8%，P=0.210）and the minimum cross-sectional area of oropharynx area increased 14.96 mm2（10.2%，P=0.481） on average . The most obvious changes on volume occurred in laryngopharyngeal, which increased 963.93mm3 (23.5%，P=0.018）. The most remarkable change of cross-sectional area occurred in velopharyngeal with an increase of 49.61 mm2 (16.6%，P=0.130). The most significant change of measures occurred in height with an increase of 1.74 mm (12.5%，P=0.010）in laryngopharyngeal. Conclusion Damon bracket and non-extraction orthodontic treatment can make effectively influence on the height and volume of laryngopharyngeal.