Abstract: Study on the influence of impurity ions in electrolyte is critical for optimizing and improving the performance of vanadium battery. Considering electrolyte materials and operation of vanadium battery,two typical ions,SiO₃^2- and Fe²⁺,were selected as the research object. The influences of SiO₃^2- and Fe²⁺ on electrochemical activity of graphite electrode and coulombic efficiency,voltage efficiency,energy efficiency and capacity attenuation of battery were investigated by cyclic voltammetry and charge-discharge test,aiming to provide theory basis for the impurity ions control in electrolyte. The results suggest that Fe²⁺ does not affect the reaction activities of the electrodes and battery efficiency,and the capacity of battery is improved by adding Fe²⁺. Nevertheless,SiO₃^2- reduces the reaction activity,voltage and energy efficiency of the electrodes and accelerates the rate of capacity attenuation of battery. Thus,SiO₃^2- should be avoided during the manufacture and use of vanadium electrolyte.