Aqueous magnesium-ion batteries have shown the desired properties of high safety characteristics, similar electrochemical properties to lithium and low cost for energy storage applications. The micro-sheet morphology of todorokite-type magnesium manganese oxide molecular sieve (Mg-OMS-1) material, which applies as a novel cathode material for magnesium-ion battery, is obtained by the simple hydrothermal method. The structure and morphology of the particles are confirmed by X-ray power diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma, scanning and transmission electron microscopy. The electrochemical performance of Mg-OMS-1 is researched by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge-discharge measurement. Mg-OMS-1 shows a good battery behavior for Mg2+ insertion and deinsertion in the aqueous electrolyte. When discharging at 10mAg−1 in 0.2moldm−3 MgCl2 aqueous electrolyte, the initial discharge capacity reaches 300mAhg−1. The specific capacity retention rate is 83.7% after cycling 300 times at 100mAg−1 in 0.5moldm−3 MgCl2 electrolyte with a columbic efficiency of nearly 100%.