A novel visible-light-responsive Ag3PO4/diatomite composite is successfully prepared by ultrasound assisted precipitation method. The structure and properties of Ag3PO4/diatomite composite are characterized by X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscope (HRTEM), N-2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (UV-vis DRS) and photoluminescence (PL). The obtained Ag3PO4/diatomite composites show enhanced photocatalytic performance for the degradation of acid brilliant scarlet dye compared with pure Ag3PO4 under visible light irradiation, and the 10%-Ag3PO4/diatomite composite exhibits the optimum photocatalytic degradation efficiency when the initial concentration of acid brilliant scarlet dye is 50 mg/L with the pH 6 and the catalyst dosage is 1 g/L, which is approximately 3.6 times higher than that of pure Ag3PO4. Meanwhile, it shows the better stability after three cycles. The enhanced performance can be attributed to the uniform dispersion of Ag3PO4 on the surface of diatomite, the stable structure, the enlarged specific surface area and the high-efficiency separation of photogenerated electron-hole pairs. Furthermore, the free radical trapping experiments indicate that h(+) and center dot O-2(-) are the major active species in the photodegradation process of acid brilliant scarlet dye. This work has the potential to provide a high-efficiency and cost-effective photocatalyst for the degradation of dye pollutants. (C) 2018 Elsevier B.V. All rights reserved.