GdB6　and　CeB6　were　used　as　raw　materials,　and　hexaborides　GdxCe1-xB6　(x=0.0　similar　to　1.0)　bulk　materials　were　prepared　by　spark　plasma　sintering　(SPS).　The　effects　of　Gd　doping　on　the　phase　composition,　the　mechanical　properties,　the　resistivity　and　the　thermionic　emission　properties　of　the　CeB6　base　material　were　studied.　The　results　show　that　high　density　GdxCe1-xB6　single-phase　block　material　can　be　obtained　with　the　sintering　parameters　including　the　temperature　1550　degrees　C,　the　pressure　50　MPa　and　holding　time　5　min.　And　the　Vickers　hardness　of　the　sintered　samples　can　reach　24.02　GPa.　The　thermionic　emission　properties　results　show　that　the　proper　amount　of　Gd　doping　can　significantly　improve　the　electron　emission　properties　of　bulk　materials.　Gd0.1Ce0.9B6　composition　block　has　the　best　thermal　emission　properties;　its　emission　current　density　is　101.57　A/cm(2),　the　zero　field　current　density　is　21.94　A/cm(2),　and　the　average　effective　work　function　is　2.34　eV　under　the　applied　voltage　condition　of　4　kV　at　1600　degrees　C,　which　are　better　than　those　of　GdB6　and　CeB6　block　samples　under　the　same　conditions.