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 Leptospirillum. ferriphilum, Acidithiobacillus. caldus and Sulfobacillus thermosulfidooxidans. 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 S8 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 Cu9Fe9S16 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.