The　surface-conduction　electron-emission　source,　based　on　planar-gate　triode　with　SnO2　film　emitters,　has　been　successfully　fabricaed　on　glass　substrate　by　magnetron　sputtering,　photolithography,　and　lift-off　technology.　The　microstructures　and　field　emission　characteristics　were　characterized　with　scanning　electron　microscopy　(SEM)　and　optical　microscopy.　Theresults　show　that　the　islands　of　tin　oxide,　about　100~300　nm　in　diameter,　were　depostied　at　the　gap　between　the　cathode　and　gate　electrode,　and　that　the　gate　voltage　was　capable　of　effectively　controlling　the　emission　and　conduction　currents.　The　electron-emission　efficiency　was　found　to　be　around　0.85%　and　the　maximun　brightness　could　reach　850　cd/m2,　indicating　that　the　SnO2　film　may　be　a　good　material　for　fabrication　of　surface-conduction　electron-conduction　electron-emission　source　based　on　planar-gate　triode.