The 1 x 1 magnesium octahedral molecular sieve (Mg-OMS-7), utilizing as cathode material in aqueous rechargeable magnesium ions batteries, is synthesized by a simple one-step hydrothermal method. Meanwhile, by changing the concentrations of H2SO4, the Mg-OMS-7 materials with controllable size and shape are obtained. To check the structure and morphology, the host materials are measured by X-ray power diffraction, scanning, transmission and high-resolution transmission electron microscopy. The electrochemical reaction mechanism is examined by cyclic voltammetry and X-ray photoelectron spectroscopy. The Mg-OMS-7 changes the morphology from micro-rugby to nano-club by controlling the concentrations of H2SO4. The nano-club Mg-OMS-7 which obtained by the 1.6 mol dm(-3) H2SO4 owns a more uniformly distribution and smaller size, which provides the shorter route for magnesium ions insert/deinsert into/from the lattice of host material and exhibits the better rate ability and cycle performance. The initial discharge capacity of this electrode can obtain 283.1 mAh g(-1) at the current density of 10 mA g(-1) in the 0.2 mol dm(-3) Mg(NO3)(2) aqueous electrolyte and the specific capacity retention rate is 94.1% after cycling 200 cycles at 100 mA g(-1) in the 0.5 mol dm(-3) Mg(NO3)(2) electrolyte.