CeB6　with　simple　cubic　CaB6-type　structure　has　attracted　much　interest　owing　to　its　promising　scientific　and　technological　characteristics　like　high　brightness,　high　melting　point,　low　vapor　pressure,　long　service　life,　and　low　work　function.　High-quality　Ce1-xGdxB6(x=0　similar　to　0.3)　single　crystals　with　ultra-low　work　function　are　successfully　synthesized　via　the　spark　plasma　sintering　combining　floating　zone　technique.　The　quality,　chemical　composition　and　thermionic　emission　properties　of　the　Ce1-xGdxB6　single　crystals　were　systematically　investigated　by　360　phi　scanning　X-ray　single　crystal　diffraction,　X-ray　fluorescence　and　emission　measurements.　Based　on　the　testing　results,　the　prepared　single　crystals　exhibit　good　quality.　The　emission　current　density　of　Ce0.9Gd0.1B6　on　(100)　crystal　surface　is　up　to　82.3　A/cm(2)　higher　than　that　of　CeB6　under　4000　V　at　1873　K,　while　the　current　density　under　zero　voltage　condition　is　24.70　A/cm(2),　about　two-fold　higher　than　that　of　CeB6.　The　average　value　of　effective　work　functions　at　different　temperatures　is　reduced　to　2.30　eV　lower　than　2.93　eV　of　CeB6.　Such　excellent　performances　suggest　that　the　ternary　hexaborides　can　be　used　as　a　promising　cathode　emitter　source　for　exploration　and　research　in　the　electron　emitter　field.