YVO4　photocatalysts　with　different　grain　sizes　were　obtained　by　annealing　the　YVO4　nanopowders　synthesized　via　microwave　irradiation.　The　products　were　characterized　by　X-ray　diffractometer　(XRD),　scanning　electron　microscope　(SEM),　transmission　electron　microscope　(TEM),　surface　area　and　porosity　analyzer,　and　ultraviolet-visible　(UV-vis)　spectrophotometer.　Photocatalytic　measurements　showed　that　the　YVO4　nanopowders　with　grain　size　of　about　5　nm　possess　superior　photocatalytic　properties　in　decolorization　of　methyl　orange　solution.　(c)　2006　Elsevier　B.V.　All　rights　reserved.