The WO₃/g-C₃N₄ composite visible photocatalysts were successfully synthesized by an ultrasound-microwave-protonation process using HCl solution as solvent. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer-Emmett-Teller (BET) specific surface area and photogradation of Rhodamine B (RhB) for visible-light properties. This results show that the composite catalysts are composed of WO₃ nanosheets loading on g-C₃N₄ nanoplates. When the mass fraction of WO₃ is 40%, the sample prepared by heating the precursor at 500℃ for 2 h has better photocatalytic activity than that prepared by pure WO₃ and g-C₃N₄. The WO₃/g-C₃N₄ can photodegradate 98% 100 mL RhB solution with concentration of 10^-5 mol/L after 5 h visible-light (wavelength is larger than 420 nm) irradiation.