The horseradish peroxidase(HRP) was fixed on the surface of glassy carbon electrode(GCE) modified by chitosan(CTS)-carboxylic multi-walled carbon nanotubes(MWNTs).The modified electrode thus prepared was named abbreviately as HRP-CTS/C-MWNTs/GCE.The HRP imbedded in the complex was characterized by fourier transform infrared spectrometry.The result indicated that its composition had no change.The electrochemical property of HRP-CTS/C-MWNTs/GCE was studied by cyclic voltammetry.It was found that the modified electrode exhibited an excellent electrocatalytic response toward the reduction of H2O2.In 1/15 mol?L-1 PBS(pH 6.98) buffer solution， a pair of redox peaks were observed,and a good linear relationship(r=0.998 6) between values of reduction peak current and H2O2 concentration was obtained in the range of 0.1-12 mmol?L-1.The method was applied in the detection of hydrogen peroxide the commercially available medical hydrogen peroxide，with content of 2.93%