A porous spherical aggregation of Li4Mn5O12 nanorods with the particle size of 3μm is prepared by oxidizing LiMn2O4 powder with (NH4)2S2O8 under hydrothermal conditions. The result displays that concentration of (NH4)2S2O8 plays a key role in forming the porous spherical aggregation and the optimal concentration of oxidant is found to be 1.5molL−1. The mechanism for the formation of the porous spherical aggregation is proposed. The electrochemical capacitance performance is tested by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge. The porous spherical aggregation exhibits a good electrochemical performance. It could deliver 375Fg−1 within potential range 0–1.4V at a scan rate of 5mVs−1 in 1molL−1 Li2SO4 and the value is cut down to less than 0.024Fg−1 per cycling period in 1000 cycles.