An electron transfer reaction between ascorbate in an aqueous solution and oxidizing agents in an organic solution immiscible with water has been studied for the first time by polarography for charge transfer at the interface between two immiscible electrolyte solutions. PL reversible electron transfer polarogram at the aqueous/organic solution interface could be observed when teterachlorobenzoquinone, dibromobenzoquinone and Meldola’s Blue were used as oxidizing agents in the organic solution. The oxidation reaction of ascorbate at the aqueous/organic interface was discussed comparing with the reactions at the ordinary electrodes and in homogeneous solutions. The half-wave potentials of electron transfer polarograms at the aqueous/nitrobenzene interface were applied to evaluate the formal redox potential of ascorbate/ascorbate free radical.