Herein is investigated the effect of ultrasonic irradiation on the preparation of Ag₃PO₄ particles based on the ion-exchange method. X-ray diffraction, scanning electron microscope, diffuse reflectance spectrum and photoluminescence were used to characterise the products. It is found that the application of ultrasonic irradiation at a frequency of 40 kHz leads to the production of uniform spherical particles with an average size of ∼300 nm. However, at a higher ultrasonic frequency of 60 kHz, the prepared sample presents polyhedron-shaped particles in the size range of 6–8 μm, which are constructed from small grains with a size of several hundred nanometres. Without the aid of ultrasonic irradiation, the samples prepared at room temperature or under 50 °C water-bath condition are composed of spherical particles and large-sized agglomerative particles. The photocatalytic activity of Ag₃PO₄ samples was evaluated by degrading rhodamine B (RhB) under simulated sunlight irradiation. Among these samples, the one prepared at 40 kHz exhibits the highest photocatalytic activity, where the degradation percentage of RhB reaches 96% after irradiation for 60 min.