The　La0.6Eu0.4B6　nanopowders　were　prepared　by　high-energy　ball　milling,　and　then　the　ball-milled　nanopowder　were　used　to　prepare　the　high-density　La0.6Eu0.4B6　polycrystalline　bulks　by　spark　plasma　sintering　(SPS).　The　influence　of　sintering　temperature　and　pressure　on　the　sample　density　and　mechanical　properties　were　investigated.　The　results　show　that　this　method　reduces　the　sintering　temperature　more　effectively　than　the　conventional　hot-pressing　method.　The　sample　density,　Vickers　hardness　and　flexural　strength　are　4.71　g/cm(3),　23.37　GPa,　and　295.14　MPa,　respectively,　which　are　also　higher　than　those　of　conventional　hot-pressing　methods.　The　thermionic　emission　results　show　that　when　the　cathode　temperature　is　1873　K,　the　maximum　emission　current　density　of　La0.6Eu0.4B6　is　33.74　A/cm(2).　Under　the　same　sintering　condition,　the　Vickers　hardness,　flexural　strength　and　thermionic　emission　current　density　of　ball-milled　nanopowder　are　increased　by　28%,　58%　and　32%　compared　with　coarse-powder-sintered　sample.　These　results　indicate　that　refining　the　powder　grain　size　to　nano　level　is　beneficial　for　reducing　the　sintering　temperature　and　promoting　the　thermionic　emission　and　mechanical　properties.