Abstract: Objective To observe the effect of diabetes on periodontitis.MethodsA diabetes periodontitis model was established and tissue sections were prepared to observe changes of morphological structure in periodontal tissue and nitric oxide（NO）was determined in gingiva.ResultsThe loss of connective tissue attachment and alveolar bone height was higher in diabetes rats with periodontitis than in periodontitis rats and normal controls（P＜0.05）.ConclusionDiabetes mellitus plays a role in promoting the damage to periodontium.