Bismuth titanate (Bi12TiO20) nanoparticles with spherical structures and good dispersion were synthesized hydrothermally using C6H13BiN2O7 center dot H2O and TiCl3 in the presence of polyethylene glycol (PEG). Only 2h of hydrothermal process was needed which means the whole process of preparation was a less power consumption. X-ray diffraction (XRD) proved that the samples were in pure cubic phase. UV-vis diffuse reflection spectra showed the band gap of Bi12TiO20 is about 2.65 eV. Brunauer-Emmett-Teller (BET) analysis showed that the Bi12TiO20 samples have higher surface areas. Visible-light-induced photodegradation of acid orange 7 (AO7) on Bi12TiO20 was investigated. It was found that Bi12TiO20-assisted photocatalytic degradation of AO7 occurs via two processes: the photocatalytic process of Bi12TiO20 semiconductor and the photosensitized process of AO7. Photocatalytic experiments in the presence of N-2 and the radical scavenger suggested that (OH)-O-center dot and 0(2)(center dot-) are two main active species in the whole degradation process. (C) 2011 Elsevier B.V. All rights reserved.