Despite high activity for photocatalytic degradation of organic dyes from water, nanoscale Ag3PO4 photocatalyst particles are difficult to synthesize. As reported in literature, Ag3PO4 particle sizes for photocatalytic degradation of water pollutants are normally larger than 100 nm. This research reports a facile and reproducible method for the synthesis of the ultrafine and uniform Ag3PO4 nanoparticles loaded on the oxygen vacated TiO2 (TiO2-OV) with average particle size as small as 2.6nm. All obtained Ag3PO4 particles can be completely loaded onto TiO2-OV support to form Ag3PO4/TiO2-OV composite photo catalysts. The prepared Ag3PO4/TiO2-OV photocatalyst exhibits much higher visible light photocatalytic activity than those of pure Ag3PO4 or Ag3PO4/TiO2 photocatalysts for the degradation of rhodamine b (Rh B) and phenol in water. After depositing thin layers of Agl on Ag3PO4 ultrafine Ag3PO4 nanoparticles, the new AgI-Ag3PO4/TiO2-OV composite photocatalysts not only show much higher photocatalytic activity, but they are also more stable than pure Ag3PO4 catalyst. This new synthesis method will provide guidelines for the preparation of ultrafine nanoparticles and highly active photocatalysts for treatment of water pollution or production of hydrogen from water splitting/reducing. (C) 2016 Elsevier B.V. All rights reserved.