To evaluate the application of nueroelectrophysiological tests in early diagnosis of sub-clinical neuropathy in diabetes mellitus (DM), The routine nerve conductive velocity (NCV),F-wave and sympathetic skin response (SSR) were detected in 27 patients with diabetes mellitus but without symptoms and signs of lesions of nerve system. Our results showed that 48.1%, 44.4 %, 51.9 % of the patients were found to have abnormal NCV, F-wave and SSR respectively. The abnormalities were mainly characterized by prolonged latency, reduced velocity and absence of wave-form.There were significant differences between the controls and the DM group (P＜0.05). Both the distal and proximal segments of nerves were affected and the distal lesions took place earlier than proximal ones and the changes in low extremities were more severe than those of upper extremities. F-wave can be used as a sensitive indicator for the early diagnosis of peripheral neuropathy and it can help to detect the subclincial lesions. SSR can be used for the evaluation of functional status of autonomic nerves in DM patients.