Bismuth oxyiodides and oxides were prepared by a solution combination with thermal treatment method. The prepared samples were characterized by X-ray diffraction, thermogravimetry, scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectra, and Brunauer-Emmett-Teller surface areas. The photooxidation activity of the samples was evaluated by photocatalytic decolorization of acid orange II under both visible light (lambda > 420 nm) and UV light (lambda = 365 nm) irradiation. Results show that a series of changes in the compounds take place during the course of calcination, described as: BiOI -> Bi(5)O(7)I -> alpha-Bi(2)O(3). Under visible light irradiation, the photocatalytic activities follow the order: BiOI > Bi(5)O(7)I > Bi(5)O(7)I/Bi(2)O(3) mixture > Bi(2)O(3), which is mainly attributed to the different absorption ability to visible light due to the different band gap energy; the activities are in the order: BiOI < Bi(2)O(3) < Bi(5)O(7)I/Bi(2)O(3) mixture < Bi(5)O(7)I under UV light irradiation, which is mainly caused by the different oxidability. (C) 2010 Elsevier Ltd. All rights reserved.