The bioleaching process is one of the promising methods for removing heavy metals from contaminated sediments. In this study the effects of sediment solid content on the performance of the bioleaching process using a mixed culture of two sulfur-oxidizing bacteria were investigated. The results showed that the rate of pH reduction decreased with increasing sediment solid content because of the buffering capacity of sediment solids. It was found that there was a linear relationship between buffering capacity and sediment solid content. For different solid contents (10-100gdm(-3)), 82-95% (w/w) of Cu; 58-70% (w/w) of Zn; 55-73% (w/w) of Mn; 33-72% (w/w) of Pb; 35-65% (w/w) of Ni and 9-20% (w/w) of Cr were leached from sediments in this bioleaching process. The rate of metal leaching was found to decrease with an increase in sediment solid content. The solubilization of heavy metal from sediments was well described by a solid content-related kinetic equation.