A high dispersed nanofiber cryptomelane-type manganese dioxide was synthesized by a facile hydrothermal reduction route. The morphological characterization was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure and electrochemical properties of the synthesized manganese dioxide were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analyses, and an electrochemical workstation (EW). A glassy carbon electrode (GCE) modified with the nanostructured cryptomelane-type manganese dioxide was investigated for amperometric detection of hydrogen peroxide (H2O2) in phosphate buffer solution with a pH 7.4 at an open circuit potential of 0.2 V. The oxidation peak current was found to increase by 1.3 μA with the addition of 0.1 mmol•L-1 H2O2 based on a MnO2 nanofiber-gelatin/GCE electrode. The amperometric signals are linearly proportional to the H2O2 concentration in the range 0.1-1.5 mmol •L-1 with a correlation coefficient of 0.996 using the GCE modified with 0.1% (w, mass fraction) cryptomelane-type manganese oxides. The sensor is sensitive and its significant electrocatalytic activity results from the nanostructure of the cryptomelane-type manganese oxides. In addition, the sensor has a good reproducibility, a low detection limit, simplicity, and a low cost of construction. These results demonstrate that this material with high electrocatalytic activity offers great promise as a new class of nanostructured electrodes for biosensors.