Aqueous rechargeable magnesium-ion batteries with low cost of magnesium resources have a potential to meet growing requirements for electric energy storage resulted from the similar electrochemical properties to lithium. The Mg1.1Mn6O12 center dot 4.5H(2)O named as magnesium octahedral molecular sieves (Mg-OMS-1) owns nanobelt structures as a cathode material for aqueous magnesium-ion battery. The morphology and structure of Mg-OMS-1 are measured by X-ray diffraction, scanning and transmission electron microscopy. The mechanism of magnesium-ion insertion/deinsertion from this host material and the theory specific capacity of Mg-OMS-1 are determined by cyclic voltammetry, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Mg-OMS-1 displays an excellent battery behavior for Mg2+ insertion and deinsertion in the magnesium-salt aqueous electrolyte. The initial discharge capacity of Mg-OMS-1 electrode can reach 248.8 +/- 0.5 mAh g(-1) at 10 mA g(-1) in the 0.2 mol dm(-3) Mg(NO3)(2) aqueous electrolyte. Even back to 10 mA g(-1) after the rate performance, the discharge capacity can achieve 214.1 +/- 0.5 mAh g(-1). The specific capacity retention rate is 90.4% after cycling 200 times at 100 mA g(-1) in the 0.5 mol dm(-3) Mg(NO3)(2) electrolyte with a columbic efficiency of 99.7 +/- 0.1% in the 5 times experiments. (C) 2016 Elsevier B.V. All rights reserved.