Objective To explore the value of plasma C-peptide levels in early prediction of type 2 diabetes mellitus with peripheral sensory neuropathy.Methods The vibration perception threshold,pain,temperature sensation,touch-pressure sensation,ankle reflex was detected in 500 eases of type 2 diabetes mellitus,and the patients were divided into 4 groups according to peripheral sensory nerve test results:normal group (159 cases),mildly abnormal group (120 cases),moderately abnormal group (121 cases) and severely abnormal group (100 cases).Fasting and 2-hour postprandial C-peptide levels were determined and analysed with peripheral sensory nerve changes.The receiver-operating characteristic (ROC) curve was used to find the best critical point for diagnosis of diabetic peripheral sensory neuropathy.Results The fasting C-peptide among 4 groups had no significant difference (F =1.632,P ＞0.05).Two-hour postprandial C-peptide from normal group to mildly abnormal group and then moderately abnormal group gradually increased [(1.110 ± 0.526),(1.324 ± 0.490),(1.573 ± 0.716) μ g/L],while 2-hour postprandial C-peptide in severely abnormal group was significantly decreased and lower than that in normal group,and there were significant differences (P＜ 0.05).The max Youden Index was 0.366 when 2-hour postprandial C-peptide was 1.173 μ g/L.Conclusions The fasting C-peptide might be not related to early diabetic peripheral sensory neuropathy,but 2-hour postprandial C-peptide might be closely related to early diabetic peripheral sensory neuropathy.It is helpful to detect the early diabetic peripheral sensory neuropathy if we can take a dynamical observation of 2-hour postprandial C-peptide.