Y2O3-doped　Mo　secondary　emitters　were　prepared　by　liquid-liquid　doping　and　solid-solid　doping,　respectively.　The　back-scattered　scanning　observation　result　indicates　that　the　emitter　prepared　by　liquid-liquid　doping　has　fine　microstructure　whereas　that　prepared　by　solid-solid　doping　has　large　grain　size.　Y2O3-doped　Mo　emitter　with　small　grain　size　prepared　by　liquid-liquid　doping　exhibits　high　emission　property,　i.　e.,　the　secondary　electron　yield　can　get　to　5.24,　about　1.7　times　that　prepared　by　solid-solid　doping.　Moreover,　Y2O3-doped　Mo　emitter　exhibits　the　best　emission　performance　among　La2O3-doped　Mo,　Y2O3-doped　Mo,　Gd2O3-doped　Mo　and　Ce2O3-doped　Mo　emitters　due　to　the　largest　penetration　depth　of　primary　electrons　and　escape　depth　of　secondary　electrons　in　this　emitter.　The　secondary　emission　of　the　emitter　with　small　grain　size　can　be　explained　by　reflection　emission　model　and　transmission　emission　model,　whereas　only　transmission　emission　exists　in　the　emitter　with　large　grain　size.