Submicron　tungsten-osmium　mixed　powders　with　the　different　content　of　Os　(atomic　number　fraction)　were　prepared　by　solid–liquid　mixing　method.　The　tungsten-osmium　mixed　matrix　disperser　cathodes　with　the　uniform　pore　structure　were　obtained　by　microwave　sintering.　The　electron　emission　testing　results　show　that,　the　addition　of　Os　obviously　improves　the　emission　performance　of　the　impregnated　tungsten-based　dispenser　cathode.　The　W–25Os　cathode　(Os　atomic　number　fraction　is　25%)　exhibits　the　relatively　low　work　function　and　high　emission　current　density.　At　1100　℃,　the　pulse　emission　current　density　of　the　W–25Os　cathode　is　42.86　A·cm−2　with　the　emission　slope　of　1.40,　which　is　1.7　times　of　the　conventional　barium-tungsten　dispenser　cathodes　under　the　same　working　conditions　and　up　to　the　electron　emission　level　of　M-type　cathodes.　The　W–25Os　cathode　shows　the　low　effective　work　function　as　1.93　eV,　which　is　conducive　to　the　generation　of　active　free　barium　source.　The　molar　ratio　of　surface　elements　Ba:(W+Os)　is　0.83:1.00,　which　is　significantly　higher　than　that　of　the　traditional　barium　tungsten　cathode　(about　0.50:1.00).　©　2023　Beijing　Research　Institute　of　Powder　Metallurgy.　All　rights　reserved.