Objective To explore the feasibility of high-frequency ultrasound detecting median nerve (MN) in type 2 diabetes mellitus(T2DM)with diabetic peripheral neuropathy(DPN).Methods Forty-two healthy volunteers were included as control group(Group A).Eighty-eight T2DM patients were divided into two groups according to symptoms,signs and electrophysiological results:with DPN (group C,46 patients) and without DPN (Group B,42 patients).The width(W),thickness(T) and cross-sectional area(CSA) of MN at 6 points [the wrist crease,pisiform bone,hamate bone,the 6 cm proximal to the wrist crease,the 4 cm proximal to tip of the medial epicondyle(ME) and the midpoint of the humerus] were evaluated.ROC curve was plotted to determine clinical diagnostic value of three lines on six points in diagnosis of DPN. Results ①Comparing with Group A,the width(P <0.05) except for the 4 cm proximal to tip of ME and the midpoint of the humerus,the thickness (P <0.05) except for the 4 cm distal to ME and CSAs of all points were enlarged in DPN patients(P <0.001).The width(P <0.05)at the wrist crease,hamate bone and the midpoint of the humerus,the thickness (P <0.01) at the wrist crease and pisiform bone,CSAs (P <0.01) of all sites except for the wrist crease were increased in Group B.Comparing Group B with C, the width at the wrist crease,the thickness in the midpoint of the humerus,CSAs except for the 4 cm proximal to ME and the midpoint of the humerus were dramaticlly increased in Group C(P <0.001).②A diagnostic value comparison:when diagnostic value of W,T and CSA at six points is the most predictive, the sensitivity is 80.4%,84.8%,84.8% respectively and specificities are all 54.8%.Diagnostic value of CSA and T is superior to the width.The CSA and T of the hamate bone level were the most predictive of DPN.The corresponding optimal cut-off value was 0.097 cm 2 ,0.233 cm respectively.Conclusions The backbone and the abnormal changes of different lines of the MN in DPN can be observed by high-frequency ultrasound.The width and thickness of the MN at six points are increased in different degree,but CSAs of all levels can enlarge.When diagnostic value of W,T and CSA at six points is the most predictive for DPN, the sensitivity is superior to specificity respectively.The CSA and T of the hamate bone levelare the most predictive for the evaluation of DPN.