Cubic　Sb2O3　nanocrystalline　was　obtained　via　a　precipitation　method.　The　sample　was　characterized　by　X-ray　diffraction　(XRD)　analysis,　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM),　UV-Vis　diffuse　reflectance　spectroscopy　(DRS)　and　electron　spin　resonance　(ESR),　etc.　The　photocatalytic　degradation　of　methyl　orange　under　UV　irradiation　as　a　model　reaction　was　used　to　evaluate　the　photocatalytic　properties　of　the　material.　The　results　revealed　that　Sb2O3　nanocrystalline　prepared　by　the　precipitation　method　exhibited　small　particle　size　and　high　photocatalytic　activity.　Factors　affecting　the　photocatalytic　activity　of　the　as-prepared　Sb2O3　nanocrystalline　are　discussed,　and　a　possible　mechanism　of　the　photocatalytic　degradation　of　methyl　orange　over　the　cubic　Sb2O3　nanocrystalline　is　also　proposed.