With Fe(NO3)3·9H2O and Bi(NO3)3·5H2O as raw materials, different sillenite-type compounds and elemental bismuth were prepared by a facile one-pot solvothermal method using H2O, C2H5OH, (CH2OH)2 and C3H8O3 as solvents, respectively. The structure, morphology, elemental compositions and properties of samples were examined by XRD, SEM, TEM, ICP, XPS, N2 adsorption and desorption, UV-vis DRS and PL. The photocatalytic activities of different samples were evaluated by the photodegradation of RhB under visible-light irradiation (l>400 nm), and results show that Bi36Fe2O57 prepared using C2H5OH as the solvent owns the optimum performance. In order to explore the reaction mechanism, an additional experiment was designed to investigate the main active species during the photodegradation process via dissolving different trapping agents in the reaction solution before light irradiation. The results show that superoxide radical anions play a major role in this system since the RhB degradation was significantly suppressed after the addition of benzoquinone.