We report graphene decorated hydrated vanadium oxide nanocomposite as an effective cathode material for long cycle-life Mg storage. Excellent electrochemical performance with specific capacity of 330mAhg−1 at low rate and stable cycling of 200 cycles with 81% capacity retention at 1Ag−1 was reported. Furthermore, the nanocomposite cathode shows a broad working temperature window from −30°C to 55°C with over 200mAhg−1 capacity at 55°C (1.0Ag−1). The charge shielding effect of crystal water in the aerogel enhances the Mg2+ insertion kinetics and the porous structure of aerogel allows easy access of electrolyte into the active material. The cycling performance, rate performance and broad temperature adaptability demonstrate that the graphene decorated vanadium oxide nanowire aerogel is a promising and attractive cathode material for practical Mg batteries.