Highly activated MnO2 nanostructure was prepared from potassium permanganate and manganese acetate, via a simple alternate drop-feeding method. This highly activated MnO2 could combust in the atmosphere of ethanol vapors to yield nanocrystalline Mn3O4 at 114 degrees C. Powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, particle size distribution, and electrochemical tests were used to characterize the as-obtained products. The results show that the as-prepared MnO2 nanostructure shows good electrochemical properties.