Recently,　high　power　magnetrons　as　the　commercial　microwave　power　source　for　various　civil　accelerators　have　gained　more　and　more　attentions　because　of　rapid　development　of　microwave　radiation　therapy　and　non-destructive　detection　[1].　Secondary　electron　emission　(SEE)　cathodes　play　an　important　role　in　the　operation　of　such　devices.　Up　to　now,　the　ordinary　secondary　electron　emitters,　such　as　Barium　dispenser　cathodes,　Oxide　cathodes,　can＇t　be　used　in　such　devices　because　of　their　non-resistance　of　violent　electron　strike　[2].　Rare　earth　oxide　Molybdenum　ceramic　(REO-Mo)　cathodes　are　considered　to　be　the　potential　emitters　for　such　magnetrons　because　of　its　excellent　secondary　electron　emission　property.　©　2010　IEEE.