In this paper a special At.f (Acidthiobacillus ferrooxidans) modified carbon powder microelectrode was prepared, and a series of electrochemical measurements were conducted to study ferrous ion Fe2 + oxidation mechanism on the electrode. CV (cyclic voltammetry) studies show that this oxidation reaction is reversible when c (Fe2 +) is lower than 0.16mol/L. At higher speed scanning, the currents through the electrode include two parts of the micro disc current and the thin layer current, while at lower speed scanning of steady state process the current provided by thin layer could be ignored, the whole oxidation reaction was controlled by diffusion process, and the calculated diffusion coefficient D0 is about 6. 25 ×10 - 6cm2.s – 1. The transient potential stair step studies also have been conducted. The results are consistence with steady state ones although thin layer currents should be taken in to account.