K4Nb6O17 photocatalyst was successfully synthesized by low-temperature hydrothermal method with layer structure. Considering that a large number of hydroxyl (Nb—OH) and oxygen species (NbO, Nb—O－) exist on the surface of K4Nb6O17 synthesized by hydrothermal method, Ag(en)+2 precursors were employed to synthesize Ag/K4Nb6O17 heterostructure photo-catalysts with highly dispersed Ag. Photocatalytic performance evaluation results show that the photodegradation rate of MO for K4Nb6O17 was remarkably improved when a small amont of Ag was loaded. The best loading dose of Ag is 0.5 at%. Based on various characterizations results of XRD, FTIR, UV-Vis DRS, XRF and TEM, the photocatalytic mechanism of Ag/K4Nb6O17 heterostructure catalysts was illuminated in detail and the conclusions were drawn as follows: (1) K4Nb6O17 nanocrystals serve as electron and hole sources for degradation of an organic dye; (2) Ag nanoparticles on the surface of K4Nb6O17 nanocrystals act as a sink for the electrons, promote interfacial charge-transfer kinetics between the metal and semiconductor, improve the separation of photogenerated electron-hole pairs, and thus enhance the photocatalytic activity of Ag/K4Nb6O17 photocatalyst.