According　to　the　principle　of　heat　conduction　during　the　operation　of　semiconductor　devices,　a　GCT　package　model　of　IGCT　devices　is　established.　Perform　transient　simulation　and　use　structure　function　analysis　software　for　analysis.　Based　on　the　thermal　resistance　and　heat　capacity　curve　obtained　by　the　structure　function　analysis　method,　the　factors　that　may　affect　the　thermal　characteristics　of　the　device　are　analyzed　from　the　two　angles　of　the　thickness　of　the　molybdenum　disk　and　the　thickness　of　the　copper　cathode.　Thermal　analysis　of　the　1µm　micro-gap　on　the　surface　of　the　molybdenum　disk　and　suggestions　for　improvement　were　put　forward.　The　research　results　show　that　the　structure　function　method　is　a　non-destructive　analysis　method　that　can　obtain　the　thermal　resistance　and　heat　capacity　of　each　layer　inside　the　device　with　high　accuracy.　The　application　of　this　method　can　analyze　the　internal　microstructure　changes　of　the　device,　and　provide　convenience　for　the　research　and　evaluation　of　the　thermal　characteristics　of　the　device.　©　Published　under　licence　by　IOP　Publishing　Ltd.