Er2Sn2O7nanoparticles　were　prepared　by　hydrothermal　method,　and　characterized　by　TEM,　XRD,　IR　and　Raman　techniques.　It　showed　that　Er2Sn2O7powder　consisted　of　compact　particles　about　20　nm　in　size　and　of　irregular　shape.　The　photocatalytic　activities　were　also　evaluated　by　decolorization　of　methyl　orange　under　ultraviolet　light.　Results　indicate　that　the　photograduation　rate　of　as-prepared　Er2Sn2O7nanoparticles　is　quite　high.　In　addition,　UV-vis,　IR,　fluorescence　techniques　were　used　to　characterize　the　degradation　species　of　methyl　orange　in　this　experiment,　and　the　possible　degradation　mechanism　was　deduced　from　the　spectral　analysis.