The electrochemistry of [octaethylporphyrin iron(III)-sigma-bonded pyrrole] (abbreviated as (OEP)Fe(II)(Pyr)) was investigated in CH2Cl2 + TBAP solution by cyclic voltammetry (CV) and in situ UV-visible electronic absorption spectrometry. It was found that (OEP)Fe(III)(pyr) can undergo a quasi-reversible one-electron reduction step to form (OEP)Fe(II)(Pyr), and two sorts of irreversible one-electron oxidation step : one was the formation of [(OEP)Fe(II)(Pyr)]+ firstly, followed by loss of the sigma-bonded pyrrole to produce [(OEP)Fe(III)]+] the other was probably the direct formation of [(OEP)Fe(III)]+ with simultaneous loss of the sigma-bonded pyrrole. It was also found that (OEP)Fe(III)(Pyr) adsorbed on the surface of glassy cardon (GC) exhibited high activity for the electrocatalytic reduction of dioxygen, but this activity was not stable. However, this catalyst can be buried in polypyrrole (PPyr) film, resulting in more stable activity. Rotation ring-disk experiments (RRDE) demonstrated that (OEP)Fe(II)(Pyr) whether adsorbed on a GC surface or buried in PPyr film could catalyze the reduction of dioxygen to give water predominantly. In these two cases, the catalytic mechanisms were found to be the same and the water production efficiencies were nearly 90% in the potential region -0.30 to 0.35 V (vs. SCE) in O2 saturated 0.05 M H2SO4 solution. The slope of the Tafel curve suggested that the one-electron transfer from [(OEP)Fe(II)(Pyr)-O2] to [(OEP)Fe(III)(Pyr)-O2-] was the rate-controlling step before the limiting disk current was reached.