Polyaniline, which was electroactive in pH5.5 NaAc-HAc buffers, was used to investigate the electrochemistry of some heme proteins. The polyaniline was electropolymerized and deposited on a macro- and a micro- platinum electrode successfully. The optimum preparation method and conditions were that the polymer film was polymerized by a galvanostatic method with 35 μA/cm2current density in a 2.0 mol/L HCl solution containing 1.0 mol/L monomer under nitrogen atmosphere. The deposit amount was about 7.0 mC/cm2for the macro- and 8.5 mC/cm2for the micro- electrode. Experimental results revealed that the commonly used heme proteins, myoglobin and hemoglobin, could exhibit useful current responses at the polymer coated electrode. Since polyaniline modified electrode have a lot of virtues such as stability, good longevity, reversibility, conductivity etc., they may be useful for protein studies in the future. Another application of the polymer is, therefore, reported in this paper.