Previously purified cytochrome c can exhibit a current response at a silver electrode and the electron transfer reaction can be promoted by dodecyl benzene sodium sulfonate. Addition of the promoter to the protein solution, the peak potentials of the protein are unchanged, but the peak currents increase sharply. Experimental results reveal that the peak current is linearly proportional to the protein concentration in the range of 0.08 – 1.2 μmol/L. The detection limit is 0.05 μmol/L. In addition, commercial samples as received can also give good redox waves after the macromolecules are acted on by the promoter. So the current response of the protein can be widely used.