The microbial oxidation of sulfide minerals in wet metallurgy has been widely studied. In recent years, the reaction between the bacterium Acidithiobacillus ferrooxidans (A.f.) and pyrite in mining environments has also aroused attention and become a focus in the study of reactions between microorganisms and minerals. In this paper, a strain of A.f. isolated from the acid mine drainage (AMD) and the mineral pyrite from the tailings of the Dabaoshan Mine were used to probe into the bio-oxidation of pyrite. Experiments were designed to compare the differences between abiotic oxidation and bio-oxidation of pyrite under different pH conditions and to investigate the effects of A.f. and pH conditions on the oxidation of pyrite.Before the experiment, the pyrite was crushed to less than 0.18 mm in size, immersed in an absolute ethyl alcohol for 30 minutes, and then washed with deionized water 3 times and put in a 50℃ vacuum drying oven for 2 hours for experimental uses. A small amount of the prepared pyrite powder was used to observe its surface morphology under a cold field emission scanning electron microscope. All the immersing experiments were then carried out in 250 mL conical flasks at a cleaning work station. A density of 3% of pulp (3 g of pyrite powder in a 100 mL solution) was added to each flask. The pyrite powder was added to a 9 K culture medium without Fe2+, inoculated with 10% (the ratio between the volume of bacterial suspension added in and that of the total solution) of A.f. suspension, and adjusted to pH 2.00 and 3.00 respectively by using 1:1 H2SO4. The experimental flasks were put in an oscillator for shaking cultures at a constant temperature of 30℃ and a rotating speed of 150 r/min, oscillating 20 hours a day. Experiments without adding A.f. suspension were also conducted at the same time for comparison.The concentrations of cations such as Fe2+, As5+ and Cd2+, anion SO42- and pH values during the experiments were measured regularly. Some of the solid experimental results were collected and dried in a 50℃ vacuum drying oven and then analyzed with XRD. A small quantity of the collected solid result was washed with deionized water 3 times, dried in a 50℃ vacuum drying oven and then investigated under a cold field emission scanning electron microscope.The experimental results showed that Fe2+, Cd2+, As5+ ions were produced by the oxidation of pyrite and that the pyrite is easier to be oxidized at pH 2 than at pH 3. The bacterium A.f. promoted the oxidation of pyrite by raising the apparent oxidation rate by 2～3 times in 30 days of the experiment. The bio-oxidations of pyrite may include indirect oxidation and contact oxidation. The results will provide valuable reference for source remediation of the AMD pollution in the Dabaoshan Mine.