Comparison in electron transfer (ET) processes from decamethyferrocene (DMFe) in nitrobenzene (NB) to ferric ion in aqueous phase was investigated for the first time by the scanning electrochemical microscopy (SECM). As compared with the system of Fe(CN)_6~(3-) -DMFe, the ET rate obtained from Fe~(3+)-DMFe was lower in spite of larger driving force, which may arise from the effect of reorganization energy. Otherwise, the effect of common ion on rate constants was also probed and results suggested additional complexity of the ET mechanism between Fe(CN)_6~(3-) and DMFe.