RE2O3-Mo/W　cathodes　were　prepared　by　powder　metallurgy　method.　La2O3-Y2O3-Mo　cermet　cathodes　prepared　by　traditional　sintering　method　and　spark　plasma　sintering　(SPS)　exhibit　different　secondary　emission　properties.　The　La2O3-Y2O3-Mo　cermet　cathode　prepared　by　SPS　method　has　smaller　grain　size　and　exhibits　better　secondary　emission　performance.　Monte　carlo　calculation　results　indicate　that　the　secondary　electron　emission　way　of　the　cathode　correlates　with　the　grain　size.　Decreasing　the　grain　size　can　decrease　the　positive　charging　effect　of　RE2O3　and　thus　is　favorable　for　the　escaping　of　secondary　electrons　to　vacuum.　The　Scandia　doped　tungsten　matrix　dispenser　cathode　with　a　sub-micrometer　microstructure　of　matrix　with　uniformly　distributed　nanometer-particles　of　Scandia　has　good　thermionic　emission　property.　Over　100　A/cm(2)　full　space　charge　limited　current　density　can　be　obtained　at　950C(b).　The　cathode　surface　is　covered　by　a　Ba-Sc-O　active　surface　layer　with　nano-particles　distributing　mainly　on　growth　steps　of　W　grains,　leads　to　the　conspicuous　emission　property　of　the　cathode.