Abstract:One acidophilic thiobacillus bacterium isolated from acid mine drainage of nickel-molybdenum was identified as Acidithiobacillus ferrooxidans (A.f) by morphological and physiological characteristics analysis. It was domesticated applying Ni-Mo ore tailings and FeSO4?7H2O as energy sources. Bioleaching of Ni-Mo ore tailings with domesticated and non-domesticated A.f was carried out in shake flasks. The results show that domesticated A.f was more conducive to leaching metals from tailings, the sequence of leaching rate of four target metals is Ni>Zn>As>Mo with the maximum extraction rate of 62.41%, 55.66%, 41.87%, and 12.04%, which is 2~8 percent point higher than that of non-acclimated group. The bioleaching mechanisms were attributed to be oxidation by bacterial and chemical solubilization by microbially-produced H and Fe3 . H plays a dominant role in leaching of Ni and Zn from tailings, while leaching of As and Mo mainly relies on continued oxidation by Fe3 .