In this paper, AgCl/Ag3PO4/diatomite photocatalyst is successfully synthesized by microemulsion method and anion in situ substitution method. X-ray diffraction (XRD), photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) are used to study the structural and physicochemical characteristics of the AgCl/Ag3PO4/diatomite composite. Using rhodamine B (RhB) as a simulated pollutant, the photocatalytic activity and stability of the AgCl/Ag3PO4/diatomite composite under visible light are evaluated. In the AgCl/Ag3PO4/diatomite visible light system, RhB is nearly 100 % degraded within 15 minutes. And, after five cycles of operation, the photocatalytic activity of AgCl/Ag3PO4/diatomite remains at 95 % of the original level, much higher than that of pure Ag3PO4 (40 %). In addition, the mechanism of enhanced catalytic performance is discussed. The high photocatalytic performance of AgCl/Ag3PO4/diatomite composites can be attributed to the synergistic effect of Ag3PO4, diatomite and AgCl nanoparticles. Free radical trapping experiments are used to show that holes and oxygen are the main active species. This material can quickly react with dye molecules adsorbed on the surface of diatomite to degrade RhB dye to CO2 and H2O. Even more remarkably, AgCl/Ag3PO4/diatomite can maintain above 95 % photo-degradation activity after five cycles.