Nanosized　ZnNb2O6　photocatalysts　(band　gaps　similar　to　4.0　eV)　were　successfully　synthesized　via　a　citrate　complex　method.　Their　particle　sizes　ranged　from　50　to　150　nm.　The　result　of　Mott-Schottky　measurement　revealed　that　the　flat-band　potential　of　ZnNb2O6　was　ca.　-1.3　V　versus　Ag/AgCl　at　pH　6.6.　The　photocatalytic　activities　of　the　samples　for　the　degradation　of　methyl　orange　were　evaluated　under　UV-light　(lambda　=　254　nm).　It　was　found　that　the　sample　obtained　at　850　degrees　C　showed　the　highest　photocatalytic　activity　due　to　its　opportune　crystallinity　and　surface　area.　Furthermore,　center　dot　OH　radicals　were　detected　as　the　major　oxidation　agents　responsible　for　the　decomposition　of　methyl　orange.