In this work, Ag3PO4was synthesized by the precipitation method using 2 different types of phosphate salts (Na2HPO412H2Oand NH4H2PO4 ) as a precipitating agent. We use visible light, the photocatalytic testing for absorption by Rhoda mine B (RhB) is mixed with a solution. Then analyzes the results by UV-Visible spectrometer. Found that when turned on the light for a long time to degrade Rhoda mine B more.