In the present study, we investigated the bioleaching of arsenopyrite with or without pyrite by moderate thermophiles. In both chemical leaching and bioleaching, the addition of pyrite decreased the leaching rate of arsenopyrite. The arsenic speciation and minerology changes in the residues were analysed by X-ray Absorption Near Edge Structure (XANES) Spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and powder X-ray Diffraction (XRD). The XANES analysis showed no detectable arsenopyrite in the final residues from the experiments without pyrite. However, there was still 21.7% of arsenic species presented as arsenopyrite after bioleaching, when the initial arsenopyrite/pyrite ratio was 1:5. The XPS analysis revealed there was only As(V) on the surface of most of the residues, except on one chemically leached sample where As(III) was found.