The electrochemical analysis was carried out by the electrochemical reduction of horse spleen ferritin (HoSF) using oxidized methyl viologen. The reduction and oxidation peaks of the methyl viologen and released Fe appeared on the cyclic voltammogram. The Fe was released on reduction of the HoSF by the methyl viologen. The effect of oxidized methyl viologen concentration and the ferritin solution pH on reduction of the HoSF were determined. The reduction of the ferritin procedure occurred by applying a potential that reduced the oxidized methyl viologen, and the HoSF was reduced by the reduced methyl viologen.