Single phase nanobelt-like Na1.2V3O8 was synthesized by precipitation from aqueous solution of V2O5, H2O2 and NaOH, and subsequent annealing at 400 oC. The product was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. As measured by both galvanostatic charging/discharging and cyclic voltammetry methods, in air-equilibrated aqueous electrolyte solutions containing nitrates of lithium, sodium and magnesium, this compound displayed fast intercalation/deintercalation reactions. The galvanostatic charging and discharging curves observed at rates ranging 500-7000mA g-1, did not display clear plateaus characteristic of phase changes. The discharging capacities were found to range 101-35, 55-17 and 67-22 mAh g-1 for Li, Na and Mg intercalation, respectively. By cyclic voltammetry, for the sweep rates increasing in the range 5-400mV s-1 (roughly 9-700C), the capacity was found to decrease within the limits 63-35 mAh g-1 for Li+ intercalation, and 40 -11 mAh g-1 for Na+ and Mg2+ intercalation, respectively. By analyzing the dependence log (current) versus log (sweep rate), the interval of potentials corresponding to preferably diffusion control of intercalation/deintercalation processes was determined.