Nanocubic　La2Sn2O7　photocatalysts　with　pyrochlore　structure　have　been　successfully　synthesized　by　a　one-pot　hydrothermal　method.　The　effects　of　alkaline　concentration,　reaction　time,　and　hydrothermal　temperature　on　the　structures　and　morphologies　of　the　resultant　products　were　investigated.　On　the　basis　of　characterization　results　from　X-ray　diffraction　(XRD),　scanning　electron　microscopy　(SEM),　transmission　electron　microscopy　(TEM),　and　selected　area　electron　diffraction　(SAED),　a　possible　growth　mechanism　of　the　nanocubes　under　the　hydrothermal　conditions　was　proposed.　The　absorption　spectra　of　as-prepared　cubic　La2Sn2O7　photocatalyst　were　determined　by　UV-vis　spectrometer.　Photocatalytic　experiments　showed　that　the　La2Sn2O7　samples　not　only　had　a　high　activity　for　degradation　of　methyl　orange,　but　also　had　the　activity　for　generating　H-2　with　a　rate　of　39　mu　mol/h　under　ultraviolet　light　irradiation.