The　large　size　high　quality　La1-xNdxB6(x=0.1-0.3)　single　crystals　had　been　successfully　prepared　by　floating　zone　melting　method　using　powder　of　LaB6　and　NdB6　as　raw　materials.　We　investigated　the　thermionic　emission　performance　of　(100)　plane　of　single　crystals.　The　single　crystals　length　was　more　than　40　mm　and　the　diameter　was　greater　than　4　mm.The　single　crystal　tests　of　diffraction　photographs,　Laue　pattern,　rocking　curves　and　fracture　SEM　images　showed　that　the　single　crystals＇　qua-lity　was　very　high.　The　thermionic　emission　results　showed　that　with　the　increase　of　Nd　content,　the　null　field　thermionic　emission　current　density　decreased　from　6.01　A/cm2　to　4.83　A/cm2　at　1　873　K,　4　000　V　and　the　average　of　effective　work　function　increased　from　2.88　eV　to　2.95　eV.　©　2017,　Materials　Review　Magazine.　All　right　reserved.