Objective: To investigate the influence of orthodontic treatment on alveolar bone height in the patients with chronic periodontitis by measuring the height of alveolar bone before and after orthodontic treatment using cone beam computer tomography（CBCT）. Methods: The distance between alveolar crest and cemento-enamel junction（CEJ） was measured by CBCT before and after orthodontic treatment of 222 teeth from patients with mild/moderate periodontal disease. Results: There were significant changes in the distance between alveolar crest and CEJ after treatment at 7 of 24 sites in the six areas of the whole mouth

including the mesial/distal aspect of maxillary anterior teeth

the mesial aspect of maxillary premolars

the mesial aspect of maxillary molars

the buccal/lingual aspect of mandibular anterior teeth

and the mesial aspect of mandibular premolars（P < 0.05）. Conclusion: Orthodontic treatment of patients with periodontal disease does not cause obvious alveolar bone absorption.