Multistage　depressed　collectors　(MDCs)　of　traveling-wave　tubes　(TWTs)　are　used　to　collect　kinetic　power　of　a　spent　electron　beam,　recover　part　of　this　power　to　a　useful　electric　power,　and,　by　such　a　way,　enhance　the　overall　efficiency　of　TWTs.　The　heat-dissipation　performance　of　MDCs　is　crucial.　This　brief　presents　a　method　for　measuring　the　heat-dissipation　characteristics　of　an　MDC　using　an　external　heat　source　and　a　heat　monitor.　This　method　uses　thermal　transient　testing　techniques　to　measure　the　thermal　contact　resistance　(TCR)　of　MDC.　A　heat　source　is　designed　to　measure　the　characteristics　of　the　MDC,　and　a　SiC　Schottky　barrier　diode　is　used　as　a　heat　monitor　to　detect　the　temperature　changes　in　real　time.　The　results　show　that　the　method　is　effective　to　measure　the　thermal　characteristics　of　the　MDC.