We report the photodegradation of rhodamine B (RhB), methyl orange (MO) and their mixture solutions at different pH values by the Ag3PO4 dodecahedrons, which are synthesized by a simple precipitation method at room temperature. The samples are characterized by X-ray diffraction spectra (XRD), scanning electron microscope (SEM) and UV-vis diffuse-reflection spectra (UV-DRS). The contrast experiments, in which dimethyl sulfoxide (DMSO) is added as the scavenger of center dot OH, confirm that the addition of acid favors the formation of more center dot OH free radicals. As a result, the higher degradation efficiency can be achieved under acidic condition than under alkaline and neutral conditions for RhB, MO and their mixture dyes. Furthermore, the Ag3PO4 dodecahedrons also show a high visible-light degradation activity for the RhB-MO mixture dye solution, in which the degradation efficiency of MO is significantly superior to that of RhB. This work could be expected to make a big step toward the practical application of photocatalysis technology. (C) 2014 Elsevier B.V. All rights reserved.