Sub-micrometer　sized　scandia,　barium,　calcium　and　aluminum　co-doped　tungsten　powders　had　been　prepared　by　spray　drying　method　combined　with　two-step　hydrogen　reduction.　The　powders　morphology,　elements　distribution,　particle　size　distribution　and　phase　transformation　process　of　reduction　were　characterized　by　scanning　electron　microscope　(SEM),　laser　diffraction　particle　size　analyzer,　energy　dispersive　spectrometer　(EDS)　and　X-ray　diffraction　(XRD),　respectively.　The　experimental　results　show　that　the　morphology　of　the　processor　powders　prepared　by　spray　drying　have　spherical　shape,　and　the　obtained　co-doped　tungsten　powders　have　the　average　size　of　around　400　nm　and　elements　distribute　evenly　in　the　powders.　The　reduction　mechanism　of　decrease　in　the　co-doped　tungsten　powders　particle　size　has　been　discussed　by　temperature　program　reduction　(TPR)　in　this　paper.