The biosorbent used for removal of Pb2+, Hg2+, and Cd2+ from aqueous solutions was rice straw fermented by Aspergillus niger (ARS), and raw rice straw (RRS) was used as a control. When inoculum size, material-water ratio, and temperature were 10(6), 100%, and 303K, respectively, the optimized spore number was 10(9). The ARS exhibited a lager pore biosorption, which was better than RRS. The biosorption mechanism was involved in chelation with functional groups such as C-H, C = O, C-O, and C = C, and the biosorption data obtained were well described by the pseudo-second-order kinetic equation and the Freundlich isotherm model.