The understandings of electrochemical reaction kinetics are significant to analytically evaluate the electrical performance of vanadium redox flow battery (VRFB). In this regard, we have conducted an experimental analysis of electrochemical reactions in a VRFB which has an active area of 25 cm2. The produced voltage and electrical current have been measured by controlling the temperature between 298 and 328 K and the flow rate from 10 to 100 mL min−1. The electrical loss is resolved to activation and ohmic losses by assuming the Tafel theory. It has been found that the electron transfer coefficient increases from 0.35 to 0.78 with increasing temperature and electrolyte flow rate, while the exchange current density can be expressed by an Arrhenius-like equation resulting in an activation energy of 8.51 kJ mol−1. The area specific resistance is evaluated in the range of 843 and 1598 mΩ cm2 depending on the temperature and electrolyte flow rate. With the evaluated electrokinetic parameters of electron transfer, exchange current density, and area specific resistance, the electrochemical losses can be successfully resolved, therefore, our analysis will be a groundwork for further improvement of electrochemical performance in VRFB.