La-LaH2　nanopowders　were　prepared　by　hydrogen　are　plasma　method,　and　then　the　mixed　nanopowders　of　La-LaH2　and　B　were　in　situ　sintered　by　Sparkle　Plasma　Sintering　(SPS)　method　in　oxygen　free　system.　High-purity　LaB6　polycrystal　nonostructured　bulk　was　successfully　synthesized　by　SPS.　The　dehydrogenation　of　LaH2　nanopowders　and　the　reaction　equation　of　sintering　LaB6　were　studied.　The　phase　and　microstructure　of　LaB6　bulks　were　characterized　by　using　XRD,　SEM,　TEM　and　AFM　techniques.　The　results　show　that　the　dehydrogenation　temperature　of　LaH2　nonopowders　is　796.4　degrees　C.　The　sintered　body　is　single-phase　LaB6,　which　has　a　high　purity　of　99.867%,　and　its　relative　densities　is　up　to　99.2%.　The　hardness　and　bend　strength　of　the　sintered　LaB6　are　much　better　than　those　of　LaB6　prepared　by　other　sintering　methods.　The　crystals　of　LaB6　Bulk　are　equiaxed　crystals,　the　average　grain　size　of　the　bulks　sintered　at　50MPs　and　1250-1350　degrees　C　is　about　120nm.　The　grains　are　homogenous　and　integrated,　and　the　grain　size　increases　with　the　raising　of　sintering　temperature.