Silver antimonite samples with different Ag/Sb ratios were prepared via ion exchange method through the mediator of silver proton-exchanged compounds. With the rise in the ratio of Ag to Sb in the samples, the optical band gap decreases due to the increasing contribution of Ag-4d to the valence band; the surface photovoltage decreases and photocatalytic activity increases due to surface states related to the Sb3+ in the samples. The present results indicate that appropriate amount of Sb3+ is favorable for improving the photocatalytic activity under visible light irradiation. (C) 2010 Elsevier B.V. All rights reserved.