In　order　to　obtain　LaB6　cathode　with　high-purity　and　excellent　properties,　La　and　LaH2　nanopowders　were　prepared　by　hydrogen　arc　plasma　method,　and　then　La-LaH2　and　B　nanopowders　were　sintered　to　fabricate　the　high-purity　LaB6　polycrystal　nano-bulk　cathode　by　in　situ　SPS　(Spark　Plasma　Sintering)　in　a　oxygen　free　system.　The　effects　of　sintering　temperature　and　pressure　on　the　phases,　microstructure　and　properties　of　the　nano-bulk　were　systematically　studied.　The　results　show　that　the　single-phase　LaB6　was　formed　in　the　nano　bulk　with　a　high　purity　of　99.867%　and　an　average　crystal　size　of　about　120　nm.　The　relative　densities　of　nano-bulk　LaB6　is　up　to　99.2%,　and　its　hardness　is　up　to　17.4　GPa,　the　bend　strength　of　the　polycrystal　LaB6　is　as　high　as　around　245.6　MPa,　the　theoretical　bend　strength　value　of　single　crystal.