Objective To explore the relationship between glycemic controls with periodontal diseases and disease conditions in patients with type 2 diabetes mellitus (T2DM).Methods Glycated hemoglobin A1c(HbA1c) and serum monocyte chemoattractant protein 1 (MCP-1) levels were measured in 34 normal subjects (control group) and 85 T2DM patients.The patients were assigned to four groups according to MCP-1 levels and complicating periodontal diseases.Both Pearson correlation analysis and univariate Logistic regression analysis were used.Results The levels of HbA1c and MCP-1 in T2DM group were significantly higher than those in control group (P ＜0.01);and the levels of HbA1c and MCP-1 in patients with periodontal disease were significantly higher than those without periodontal disease (P ＜ 0.01).In both normal MCP-1 with periodontal diseases and elevated MCP-1 without periodontal diseases groups,HbA1c level was significantly higher than that in normal MCP-1 without periodontal diseases group (P ＜ 0.01).In elevated MCP-1 with periodontal diseases group,patients had significantly higher HbA1 c levels than that in either periodontal diseases group or elevated MCP-1 group,respectively (P ＜ 0.01).In HbA1c≥7.0％ group,MCP-1 levels and the incidence of periodontal diseases were significantly higher than that in HbA1c ＜7.0％ group (P ＜0.01).HbA1c levels were positively correlated with MCP-1 levels in HbA1c≥7.0％ group (R2 =0.6004,P ＜ 0.01).Univariate regression analysis showed that HbA1c ≥7.0％ was the risk factor for complicating periodontal diseases in T2DM patients (OR =1.65,95％ CI:1.12 ～ 2.56,P ＜ 0.01).Conclusions Poor glycemic control is related to periodontal disease and the disease conditions in T2DM patients.Elevated HbA1c levels can be used as the assessing indicator for periodontal diseases of T2DM patients.