Nanometer-(70-80　nm)　and　micrometer-sized　(500-600　nm)　rare-earth　(RE)　oxides　(La2O3,　Y2O3)　were　separately　mixed　with　tungsten　powder　by　a　mechanical　alloying　method.　Afterwards,　the　W-1.5La(2)O(3)-0.1Y(2)O(3)-0.1ZrO(2)　(wt%)　was　prepared　by　cold　isostatic　pressing,　medium-frequency　induction　sintering,　rotary　forging,　and　drawing.　Then　we　performed　tungsten　argon　arc　welding　(TIG)　under　the　same　welding　current　for　0.5,　1,　and　2　h　on　the　cathode　samples　containing,　separately,　nanometer-　and　micrometer-sized　RE　oxides.　Results　show　that　the　sample　with　nanometer-sized　RE　oxides　exhibits　higher　working　stability　during　the　welding　process,　and　the　burning　loss　is　decreased　by　nearly　85.4%.　Moreover,　with　prolonging　the　working　time,　the　aggregation　degree　of　RE　oxides　in　different　regions　of　the　tip　significantly　increases.　Combined　with　the　temperature　simulation　by　COMSOL　Multiphysics,　we　found　that　the　diffusion　activation　energy　of　the　second　phase　is　decreased　by　nearly　34%.　This　is　because　the　finer　second　phase　effectively　controls　the　evolution　of　the　tungsten　matrix　structure,　thus　preserving　many　grain　boundaries　as　channels　and　promoting　the　diffusion　of　active　substances.