Photonic　crystals　of　multiple　metal　oxides　with　highly　ordered　structures　and　unique　photonic　effects　have　presented　a　prospective　application　in　designing　of　photocatalysts.　In　this　study,　a　facile　method　was　developed　to　prepare　pure　ZnGa2O4　photonic　crystals　with　a　highly　ordered　skeleton　structure　at　a　relatively　low　temperature　(500　degrees　C).　Due　to　facilitated　mass　transport　in　a　highly　ordered　channel,　the　asprepared　ZnGa2O4　photonic　crystals　exhibits　better　photocatalytic　activity　towards　methyl　orange　degradation　compared　to　those　of　porous　ZnGa2O4　and　ZnGa2O4　nanocrystals.　By　changing　the　pore　diameters　in　the　structure,　a　slow　photon　effect　on　the　blue　edge　of　photonic　band　gap　could　be　observed,　which　consequently　enhanced　the　electronic　band　absorption　over　ZnGa2O4　photonic　crystals　with　a　pore　diameter　of　180　nm,　and　further　improved　their　corresponding　photocatalytic　activity.　Furthermore,　the　degradation　mechanism　over　ZnGa2O4　photonic　crystals　was　discussed.　The　preparation　of　ZnGa2O4　photonic　crystals　in　this　study　provides　experimental　guidance　for　developing　ternary　metal　oxide　photonic　crystals　with　enhanced　light　absorption　and　photocatalytic　activities.