InVO4　is　a　new　developed　visible　light　responding　photocatalyst　for　water　decomposition,　which　is　obtained　by　a　solid-state　reaction　at　high　temperature　traditionally.　In　this　paper,　pure　InVO4　nano-crystalline　powder　has　been　prepared　by　a　hydrothermal　process　at　low　temperature　and　was　characterized　by　TEM,　IR,　and　X-ray　diffraction.　Many　factors　such　as　pH　value,　reaction　time　and　temperature　have　been　investigated.　It　is　found　that　the　optimal　conditions　for　the　preparation　is:　n　InCl3　nNaVo3=1:2;　temperature　:　150°C;　Reaction　time:　4-8　h;　pH=　7.9-8.0.　And　the　experimental　result　shows　that　it　is　a　convenient　way　to　get　single　dispersing　InVO4　nano-crystalline　powder　by　flux　in　alkyl　alcohol.