Ti-supported IrO(2)(x) + MnO(2)(1-x) coatings were prepared by thermal decomposition of a mixture of H(2)IrCl(6) and Mn(NO(3))(2) dissolved in hydrosolvent. The nature and oxygen evolution reaction (OER) mechanism of the IrO(2) + MnO(2) electrodes in 0.5 M H(2)SO(4) solution was studied by EIS measurements, emphasizing on the influence of coating composition, preparation temperature and the reaction potential. A mathematical simulation of experimental EIS data was carried out based on one state-variable theory. The simulated numerical number deduced the IrO(2)(x) + MnO(2)(1-x) coating nature and oxygen evolution reaction mechanism during the process Of 02 evolution. The inner relationships of coating nature with coating composition, and preparation temperature, the reaction potential, were analyzed and founded by these parameters of the R(s), R(f), C(f), R(ct) and C(d1). The C(d1) and 1/R(ct) parameters have the high reliability in measuring the electrochemical activity of the IrO(2)(x) + MnO(2)(1-x) oxide electrodes for OER, which can extend to that of other oxide electrodes. (C) 2008 Elsevier B.V. All rights reserved.