Abstract: In order to clarify the function of quartz in chalcopyrite bioleaching,quartz with particle sizes less than 43 μm was used to prepare a slurry system with chalcopyrite and pyrite for studying the effect of the mass concentration of quartz on the bioleaching efficiency of chalcopyrite.It is shown that the bioleaching of chalcopyrite can be improved by the addition of proper amount of quartz with finer particle sizes.Under the addition of 50 g·L^-1 quartz whose particle size was less than 43 μm,the largest leaching rate of chalcopyrite is 54.09%.Based on the analysis of oxidation-reduction potential,pH values,Fe²⁺ and Fe³⁺ mass concentrations and the results of scanning electron microscopy and energy dispersive spectroscopy,quartz benefits the bioleaching of chalcopyrite,and this phenomenon mainly presents a decrease of bioleaching delay time.Moreover,new precipitates generated in the leaching process can be adsorbed by quartz,which reduces the hindrance of precipitation during chalcopyrite bioleaching.