Abstract: Objective To study the correlation between glycosylated hemoglobin（HbA1c） and complications of diabetes mellitus. Methods Concentration of HbA1c and blood sugar was measured in 100 diabetes mellitus patients（diabetes mellitus group） and 90 healthy volunteers（control group）. The correlation between HbA1c and complications of diabetes mellitus was analyzed by SPSS. Results The concentrations of HbA1c and average blood sugar were significant higher in diabetes mellitus group than in control group（P＜0.01）. The average levels of HbA1c and blood sugar were significant higher in diabetes mellitus patients with complications than in those without complications（P＜0.01）, suggesting that HbA1c was positively related with the average concentration of blood sugar in diabetes mellitus patients（P＜0.01）. Conclusion HbA1c is positively related with the complications of diabetes mellitus. Assay of HbA1c helps to monitor the occurrence of chronic complications of diabetes mellitus.