The present work was performed in order to evaluate methanesulfonic acid (MSA) as electrolyte medium for V(IV)/V(V) redox couple as positive species applied in redox flow battery (RFB). V-MSA solutions containing more than 3.0 mol L-1 vanadium ions were obtained. Conductivity and viscosity of 3.0 mol L-1 V(IV)/V(V) electrolyte were determined to be 0.10 cm s(-1) and 12.37 mPa s respectively. Cyclic voltammetry was conducted to investigate the electrochemical behavior of V(IV)/V(V) redox couple. The diffusion coefficients of V(IV) on Pt electrode in 1.0, 2.0 and 3.0 mol L-1 V(IV)/V(V) electrolytes determined were 3.606 x 10(-6), 1.813 x 10(-6) and 0.5244 x 10(-6) cm(2) s(-1), respectively. A Zn-V battery was assembled with V(IV)/V(V)-MSA positive species and Zn/Zn(II)-MSA negative species. The cell voltage in charged state was 1.9-2.0 V and discharge voltage reached up to 1.7 V. The average coulombic efficiency and energy efficiency of the assembled cell were 95.85% and 63.90% respectively and it showed a good cyclic charge-discharge performance, which indicates that MSA has a promise application prospect in vanadium redox battery. (C) 2012 Elsevier Ltd. All rights reserved.