THz　technology　has　attracted　great　attention　for　decades　of　years.　Among　the　wide　research　areas　of　THz　technologies,　vacuum　electron　terahertz　radiation　sources　have　obvious　advantages　in　high　power　region.　For　the　THz　vacuum　electro　devices　(VED),　high　current　density　electron　beams　with　small　dimensions　are　required.　Nanosized　scandia　doped　dispenser　(SDD)　cathodes　have　the　capability　to　operate　stably　at　pulsed　current　densities　of　over　100　A/cm(2)　at　950　degrees　C　so　it　becomes　the　most　promising　cathodes　to　meet　the　requirements　for　THz　VEDs.　In　this　paper,　we　report　a　new　approach　for　developing　miniaturized　electron　beam　sources　on　normal　SDD　cathodes.　An　electron　beam　of　400　mu　m　in　diameter　has　been　directly　generated　on　an　SDD　cathode　by　deposition　of　a　Zr/W　double-layer　anti-emission　film　and　followed　by　a　focused　ion　beam　(FIB)　milling.　Results　indicate　that　the　electron　beam　is　able　to　provide　a　space　charge　limited　(SCL)　current　density　of　over　50　A/cm(2)　at　the　operating　temperature　of　950　degrees　C　with　proper　laminarity　and　works　stably　for　more　than　1000　hours.　The　beam　emission　characteristics　and　the　function　of　the　anti-emission　film　have　been　discussed　and　related　to　the　surface　analysis　results.　The　approach　opens　a　new　way　for　producing　high　emission　mini-electron　sources　to　satisfy　the　requirment　of　THz　VEDs.