Two　types　of　secondary　emitter　materials,　the　rare　earth　oxides　(RE2O3)　doped　Mo　cermet　cathodes　and　the　Y2O3-W　matrix　pressed　cathode,　are　introduced　in　this　paper.　According　to　the　calculation　results,　Y2O3　exhibits　the　best　secondary　emission　property　among　Y2O3,　La2O3,　CeO2　and　Lu2O3.　The　rare　earth　oxides　co-doped　Mo　cathodes　in　which　Y2O3　is　the　main　active　substance　exhibit　better　secondary　emission　property　than　single　RE2O3　doped　Mo　cathode.　The　results　obtained　by　the　Monte-Carlo　calculation　method　show　that　the　secondary　electron　emission　property　is　strongly　related　to　the　grain　size　of　the　cathode.　The　decreasing　of　the　grain　size　reduces　the　positive　charge　effect　of　the　rare　earth　oxide　due　to　the　electrons　supplement　from　the　metal　to　the　rare　earth　oxide,　whereby　the　secondary　electrons　are　easier　to　escape　into　the　vacuum.　Y2O3　is　introduced　into　Ba-W　cathode　to　fabricate　a　pressed　Y2O3-W　matrix　dispenser　cathode.　The　result　indicates　that　the　secondary　emission　yield　of　the　Ba-W　cathode　increases　from　2.13　to　3.51　by　adding　Y2O3,　and　the　thermionic　emission　current　density　(J(0))　could　reach　4.18　A/cm(2)　at　1050　degrees　Cb.