In this study, bioleaching experiments, synchrotron X-ray Diffraction (XRD), synchrotron X-ray Photoelectron Spectroscopy (XPS) and X-ray absorption near edge spectra (XANES) were conducted to investigate the intermediates and surface species of bornite leached by mesophilic mixed bacteria of <I>Leptospirillum. ferriphilum</I>, <I>Acidithiobacillus. caldus</I> and <I>Sulfobacillus thermosulfidooxidans</I>. The dissolution of bornite bioleaching in this study occurs in three stages. Firstly, only small amount bornite dissolved in the first two days and small amount CuS and S<SUB>8</SUB> were formed.Secondary, crystal structure of bornite changed significantly. With the dissolution of bornite, a large amount of CuS was formed. Thirdly, with the dissolution of CuS a large amount of Cu<SUB>9</SUB>Fe<SUB>9</SUB>S<SUB>16</SUB> was formed. The fitted results of XANES spectra showed that the structure of bornite changed dramatically. Bornite would convert to a chalcopyrite-like Fe-contained copper sulfide and covellite. The presence of polysulfide and element sulfur did not inhibit the bornite bioleaching.