Ten 7-week-old female C57BL/6 mice were randomly divided into control group（n=5）and chronic periodontitis group（n=5）.The chronic ?periodontitis?models of mice were induced? by? oral? infection? with P.gingivalis. The resorption of alveolar bone of the mice in two groups was estimated by measuring the distance from the cemento-enamel junction（CEJ） to the alveolar bone crest（ABC）；HE staining was performed to examine the infiltration of inflammatory cells， attachment loss of connective tissue and resorption of alveolar bone in periodontal tissue of the mice in two groups.? flow cytometry was used to detect the percentages and number of F4/80^＋iNOS^＋ M1 macrophages in gingival tissue of the mice in two groups； real-time quantitative PCR method was used to detect the expression levels of iNOS mRNA in gingival tissue of the mice in two groups.

Compared with control group， the distance from CEJ to ABC of the mice in chronic periodontitis group was increased significantly（P<0.01）； the gingival junction epithelium attached to the root side of CEJ， and the absorption of ABC became flat， the osteoclasts and bone resorption lacunae of the mice in chronic periodontitis group were found.The number and percentage of M1 macrophages in gingival tissue of the mice in chronic periodontitis group were significantly higher than those in control group（P<0.01）.Compared with control group，the expression level of iNOS mRNA in gingival tissue of the mice in chronic periodontitis group was significantly increased（P<0.01）.

In the mouse model of chronic periodontitis， the immune response mediated by M1 macrophages is enhanced， and M1 macrophages are involved in the inflammatory response and tissue damage of chronic periodontiti.