In this work, vertically aligned -MnO2 nanosheets on carbon nanotubes are synthesized simply by a solution process and the electrochemical performance as host materials of magnesium ion is tested in aqueous solution. Cyclic voltammetry analysis confirms the enhanced electrochemical activity of carbon nanotube-supported samples. Moreover, carbon nanotubes skeleton could reduce the charge transfer resistant of the cathode materials, which is confirmed by electrochemical impedance spectroscopy. Furthermore, when tested as magnesium ion batteries cathodic electrode, the -MnO2/carbon nanotube sample registers a prominent discharge capacity of 144.6mAh g(-1) at current density of 0.5A g(-1), which is higher than the discharge capacity of -MnO2 (87.5mAh g(-1)) due to the synergistic effect of insertion/deinsertion reaction and physical adsorption/desorption process. After the 1000th cycle, a remarkable discharge capacity of 48.3mAh g(-1) is collected for -MnO2/carbon nanotube at current density of 10A g(-1), which is 85% of the original. It is found that the carbon skeleton not only improved the capacity but also enhanced the cycling performance of the -MnO2 electrode significantly. Therefore, -MnO2/carbon nanotube is a very promising candidate for further application in environmentally benign magnesium ion batteries.