Abstract: Objective To study the reference value of HbA1c for diagnosis of type 2 diabetes mellitus（DM）and compare the sensitivity and reliability of glycosylated albumin（GA-L） and HbA1c in diagnosis of type 2 DM. Methods Five hundred and nine patients with type 2 DM（268 males and 241 females） were diagnosed according to the diagnostic criteria of American Diabetes Association（ADA）.The sensitivity and reliability of GA-L and HbA1c in diagnosis of type 2 DM were analyzed and compared by plotting the receiver operating characteristic（ROC） curve for DM. Results The optimal cut point of HbA1c for diagnosis of type 2 DM was 6.75% with a sensitivity of 75.5% and a specificity of 93.2%.The area under the ROC curve was 0.886 with a positive likelihood ratio of 5.45 and a negative likelihood ratio of 0.23,a positive predictive value of 92% and a negative predicative value of 70%.The optimal cut point of GA-L was 17.45% with a sensitivity of 70.1% and a specificity of 91.6%.The area under the ROC curve was 0.844.When the optimal cut point of HbA1c and GA-L was ≥6.75% and ≥17.45%,its diagnosis accuracy was 94.9% and 93.3% respectively. Conclusion The HbA1c ≥6.75% and GA-L ≥17.45% can be used the reference values for the diagnosis of type 2 DM.The sensitivity and specificity of HbA1c are higher than those of GA-L in diagnosis of type 2 DM.