This　paper　investigates　a　nondestructive　method　to　measure　the　heat　dissipation　capability　of　slow-wave　structure　(SWS)　of　helix　traveling-wave-tube　(TWT).　Bases　on　the　transient　temperature　rise　measurement　technology,　the　thermal　resistance　model　is　established　for　accurate　prediction　of　the　heat　dissipation　of　the　SWS.　And　the　thermal　resistances　in　different　positions　of　the　SWS　are　acquired.　The　results　show　that　the　difference　of　thermal　resistances　along　the　SWS　reaches　73.9%.　The　method　can　therefore　provide　the　engineering　designers　with　relatively　accurate　and　reliable　prediction　data　to　investigate　the　thermal　characteristics　of　SWS　and　exclude　the　failure　products　of　helix　TWT.