Y2O3-doped Mo secondary emitters were prepared in both liquid and solid forms. The solid preparation showed better microstructure than the liquid one. The small-grain size Y2O3-doped Mo emitter exhibited high emission properties, with a secondary electron yield up to 5.24, about 1.7 times higher than the solid preparation. Among various emitters, Y2O3-doped Mo emitter showed the best emission performance in terms of electron penetration depth and escape depth. The emission properties of small-grain size emitters can be explained by emission models, with only escape emission present in large-grain size emitters.