Acidithiobacillus ferrooxidans plays an important role in the pyrite oxidation process and has been widely studied in order to determine the kinetics of the reactions, but the details of the oxidation processes on the surface of pyrite keeps poorly known. In this study, the bio-oxidation process of pyrite by Acidithiobacillus ferrooxidans was studied by comparing with abiotic oxidation by Fe3+. The attachment of Acidithiobacillus ferrooxidans on pyrite surface was found by using Scanning Electron Microscope and Fluorescence Stereo Microscope. Analysis of the concentration of increased total iron ion suggested that the rate of biooxidation was higher than that of abiotic oxidation. Corrosion morphologies on bio-oxidized pyrite surface were deeper than that of abiotic oxidation. Especially, some corrosion holes on bio-oxidized pyrite surface were oriented and cell-shaped, and this indicated that pyrite biotic erosion should be closely related with attachment of bacteria on mineral surface.