The design and architecture of the nanoheterostructure composites was a key aim of material scientists owing to the central role of the composites in the improvement in photogenerated charge separation and quantum efficiency. The Ag/Ag3PO4/graphene triple heterostructure composites were fabricated in situ by the redox reaction between Ag+ and graphene. The structural evolution of these heterostructures was characterized by using XRD and TEM. The XPS and surface photovoltage spectroscopy revealed the photogenerated electron–hole pair’s transmission process within the composites. The Ag/Ag3PO4/graphene triple heterostructure could improve the charge separation rate under visible-light irradiation. Simultaneously, the photocorrosion phenomenon can be inhibited effectively by the triple heterostructure, which leads to the high structural stability for photocatalysis. Graphene’s fine adsorption performance for O2 and organic pollutants is also an important factor in improving the photocatalytic efficiency. Thus, the novel Ag/Ag3PO4/graphene triple heterostructure demonstrates improved photocatalytic activity and structural stability under visible-light irradiation. This facile and straightforward method has promising applications in the fabrication of different graphene-based heterostructure photocatalyses.