The deep eutectic solvent (DES) can be used as a non-aqueous electrolyte that has unique advantages such as wide electrochemical window, low vapor pressure and easy preparation.The electrochemical characteristics of a redox couple and the transport properties of corresponding ions in the DES determine the availability of this redox couple in non-aqueous flow batteries.In this work, the electrochemical characteristics of Ⅴ(Ⅱ)/Ⅴ(Ⅲ) redox couple and the transport properties of vanadium ions in the Reline DES are studied.The cyclic voltammetry (CV) curves on a glassy carbon electrode show that at room temperature the redox reaction is quasi-reversible with the charge transfer coefficient of 0.39.The transport properties of vanadium ions, including the diffusivity, viscosity, conductivity in the Reline DES at different temperatures, are also measured.The results indicate that the transport properties are comparable to that in the conventional ionic liquids.The high solubility of vanadium ions in the Reline DES can be attributed to the formation of hydrogen bond donor, which is confirmed by the FT-IR absorption spectra analysis.This study reveals that the Ⅴ(Ⅱ)/Ⅴ(Ⅲ) redox couple is promising to be applied in a eco-friendly, low cost flow battery with Reline DES as electrolyte.