The Ag/g-C₃N₄/ZnO ternary composite photocatalytic materials with excellent photocatalytic properties were successfully prepared by a facile two-step hydrothermal method. The morphologies and properties of the materials were tested by SEM, TEM, XRD, XPS and UV-Vis diffuse reflectance spectroscopy. The results of SEM and TEM showed that the sea urchin-like ZnO based ternary composite materials self-assembled from screw rod-like ZnO. The analysis of XPS confirmed the presence of dual heterojunction among Ag,g-C₃N₄ and ZnO. A large red-shift of the light absorption edge was appeared in the composite materials compared with pure sea urchin-like ZnO. The photocatalytic experiments under the irradiation of xenon lamp showed that the photocatalytic performance of the material was tremendously enhanced, and the degradation degree of RhB solution reached 97%. The unique performance caused by the special morphology of nanostructured Ag/g-C₃N₄/ZnO, the local surface plasmon resonance (LSPR) effect of Ag nanoparticles and the formation of heterojunctions between g-C₃N₄ and ZnO had been investigated.