Abstract Ag 3 PO 4 photocatalyst was prepared by precipitation method and characterized by SEM, XRD and diffusive reflectance UV–vis (DRUV–vis) absorption spectra. The gas-phase photodegradation of volatile organic compounds (VOCs) such as benzene and acetone, and the liquid-phase photodegradation of the cationic and anionic dyes on Ag 3 PO 4 were systematically investigated. Both benzene and acetone could not be photodegraded on the Ag 3 PO 4 photocatalyst under the visible irradiation. The Ag 3 PO 4 photocatalyst is efficient for the photodegradation of the aqueous dye solutions, but could not completely photomineralize the dyes to CO 2 and H 2 O. The reason is discussed by comparing the oxidation potential of organic pollutants and the potential of photogenerated holes in Ag 3 PO 4 , and measuring the absorption of organic pollutants on Ag 3 PO 4 . The photostability of the Ag 3 PO 4 photocatalyst for the photo-degradation of the dyes was tested. The Ag 3 PO 4 photocatalyst itself is photostable in the absence of the scavenger of the photogenerated holes, but is photocatalytically instable in the liquid-phase photodegradation of dyes due to the photoreduction of Ag + in Ag 3 PO 4 to Ag.