A highly crystalline macroporous β-MnO2 was hydrothermally synthesized using stoichiometric reaction between KMnO4 and MnCl2. The as-prepared material has a pore size of ca. 400nm and a shell thickness of 300–500nm. The formation of the macroporous morphology is related to self-assembling from nanowires of α-MnO2, and could be obtained at high reactant concentrations (e.g., 0.8M KMnO4) but not at low ones (e.g., below 0.04M KMnO4). Compared to conventional bulk β-MnO2 processing very low capacity, our macroporous material exhibits good electrochemical activity, e.g., obtaining an initial discharge capacity of 251mAhg−1 and sustaining as ca. 165mAhg−1 at 10mAg−1. The electrochemical activity of the as-prepared β-MnO2 is related to its macroporous morphology and small shell thickness; the former leads to that electrolyte can flood pore of the material and its inner surface is available for lithium ion diffusion, while the latter helps to release the stress from phase transformation during the initial discharging. The X-ray diffraction characterizations of the macroporous β-MnO2 electrodes suggest that, upon initial discharging, such a β-MnO2 will be irreversibly transformed to an orthorhombic Li x MnO2 and then cycled within the new developed phase in the subsequent lithium insertion/extraction processes.