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　(　Nb=O,　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.