The　polycrystalline　rare-earth　hexaborides　(BaxGd1-x)B-6　(x　=　0,　0.2,　0.4,　0.8)　were　prepared　by　the　reactive　spark　plasma　sintering　(SPS)　method　using　mixed　powder　of　BaH2,　GdH2　and　B.　The　effects　of　Ba　doping　content　on　the　crystal　structure,　the　grain　orientation　and　the　thermionic　emission　properties　of　the　GdB6　were　investigated　by　X-ray　diffraction,　electron　backscattered　diffraction　and　emission　current　measurements.　It　is　found　that　all　the　sintered　samples　exhibit　high　densification　(＞　97%)　and　high　value　of　Vickers　hardness　(2070　kg/mm(2)).　The　maximum　thermionic　emission　current　density　of　GdB6　is　11　A/cm(2)　at　a　cathode　temperature　of　1873　K,　which　is　much　higher　than　that　of　traditional　method.　With　the　increase　of　Ba　content,　the　thermionic　emission　current　density　decreases　from　11　A/cm(2)　to　2.25　A/cm(2)　at　1873　K.