Objective To explore the effect of serum C-peptide as well as glycated hemoglobin(HbA1c)in the diagno-sis of diabetes mellitus.Methods 96 diabetic patients admitted to the 910th Hospital of the United Logistics Force from January 2022 to May 2023 were selected as the diabetic group,and 60 healthy personnel who underwent physi-cal examination were selected as the control group,all of whom were tested for serum C-peptide and HbA1c,and the results of the two groups were compared.Results Compared with the control group,the diabetic group had lower se-rum C-peptide and higher HbA1c levels,and the differences were statistically significant(both P<0.05).The accuracy of serum C-peptide combined with HbA1c in diagnosing diabetes was 87.18%,sensitivity was 85.42%and specificity was 90.00%.Conclusion Serum C-peptide as well as HbA1c in the diagnosis of diabetes mellitus can achieve better results,and at the same time,it can provide reference value for the assessment of diabetes mellitus patients.