Herein, a novel visible-light responsive Ag/Ag3PO4/diatomite composites was successfully fabricated through a Deposition-Hydrothermal-Photoreduction method by using diatomite as the substrate. The crystal structure and morphology of the as-prepared samples were characterized by XRD, SEM, EDS and TEM. It can be found that a large number of spherical Ag/Ag3PO4 nanoparticles evenly loaded the surface of the diatomite substrate. The photocatalytic performances of the Ag/Ag3PO4/diatomite composites were evaluated by degradation RhB under visible-light irradiation (λ ≥ 420 nm). The effect of the adding amount of diatomite on the photocatalytic activity of the composite was also analyzed. The results indicated that the Ag/Ag3PO4/diatomite composites exhibit highest photocatalytic activity when the adding amount of diatomite reached 20%. The degradation rate of the Ag/Ag3PO4/diatomite-20% composites to RhB is as high as 90%, and the photoreaction kinetics constant value of the Ag/Ag3PO4/diatomite is 0.0371 which is 4.25 times higher than that of pure Ag3PO4 nanoparticles. Moreover, the mechanism of catalytic performance enhancement also has been discussed, the high photocatalytic performance of the Ag/Ag3PO4/diatomite composites can be attributed to the synergistic effect of Ag3PO4, diatomite and Ag nanoparticles. The radical trap experiments indicated that holes and O2− were served as the main active species. The Ag/Ag3PO4/diatomite composites synthesized via a facile and cost-effective route is a promising candidate in organics removal. Display omitted •A novel Ag/Ag3PO4/diatomite composites were successfully synthesized.•The photocatalysis performance of the composites were studied under visible light.•The presence and influence of Ag3PO4 particles in diatomite matrix was systematically analyzed.•The Ag/Ag3PO4/diatomite composites exhibit excellent photocatalytic activity and stability.