A novel series of photocatalysts, bismuth oxyhalide (BiOX, X = Cl, Br, and I), were synthesized by a hydrolysis method. The powder samples were characterized by the use of X-ray diffraction (XRD), scanning electron microscope, and UV-Vis spectrophotometer. The XRD pattern showed that all the BiOX were well crystallized in the tetragonal structure. The band gaps of the sheet-shaped compounds BiOX (X = Cl, Br, and I) were 3.44, 2.76, and 1.85 eV, respectively. BiOBr showed the highest photocatalytic activity in degrading rhodamine B (RhB) and evolving O2 for its proper valence band (VB). BiOI has no photocatalytic activity. BiOCl showed the highest activity in decomposing isopropanol because of electron-hole pair separation through trapping electrons by oxygen vacancies. © 2008 The Nonferrous Metals Society of China.