Objective To study the prevalence of Tannerella forsythensis（T.forsythensis） in the subgingival plaque of type 2 diabetes, analyze the relationship between T.forsythensis and related factors, discuss the role of T.forsythensis in the chronic periodontitis and type 2 diabetes. Methods 160 subgingival plaque samples were collected from type 2 diabetic patients and pathogens genomic DNA were extracted by phenol and chloroform from plaque. T. forsythensis was detected by polymerase chain reaction, and Pearson correlation and Logistic regression analysis were used to analyze the relationship between T.forsythensis and systemic factors and periodontal status. Results The prevalence of T. forsythensis in mild, moderate, severe periodontitis group was 47.82%, 48.71%, 67.39% respec - tively, and the prevalence was higher in the severe periodontitis group than in mild, moderate group（P
