Abstract: Objective To study the alveolar bone changes before and after periodontal treatment via measuring the changes in alveolar bone height and density by cone beam CT (CBCT) in patients with chronic periodontitis. Methods We selected 100 cases of chronic periodontitis patients in Lishui city second people's hospital from January,2013 to December,2015 for the study.All patients were given periodontal treatment.The changes in alveolar bone height and density were measured by using CBCT. Results The alveolar bone density of mild periodontitis patients were higher than those of moderate periodontitis and severe periodontitis patients both before and after the treatment (P<0.05).The alveolar bone density all increased after the treatment in mild,moderate,and severe periodontitis patients (P<0.05).Both before and after treatment,the alveolar bone loss of mild periodontitis patients was less than that of moderate periodontitis (P<0.05),and moderate periodontitis less than severe periodontitis (P<0.05).The alveolar bone loss after the treatment in mild periodontitis,moderate periodontitis and severe periodontitis patients were marginally higher than those before the treatment,but the difference was not statistically significant (P>0.05).The anterior alveolar bone density after the treatment was not improved significantly,the difference was not statistically significant (P>0.05).The premolars and molars alveolar bone density after the treatment were improved significantly (P<0.05).The alveolar bone loss of anterior teeth,premolars and molars after the treatment were not improved significantly (P>0.05). Conclusion The periodontal treatment can improve alveolar bone density in patients with chronic periodontitis.CBCT scan can be used to assessing alveolar bone mass before and after the periodontal treatment.