A　novel　IGBT　3-D　thermal　model　is　implemented.　The　thermal　distribution　is　simulated　and　analyzed　by　using　the　Finite　Element　Method　-　based　analytical　software　ANSYS.　Simulation　results　show　that　thermal　coupling　aggravate　the　self　-　heating　of　the　device,　it　is　becoming　to　select　10　μm　distance　between　cells,　Temperature　dependent　thermal　conductivity　of　Si　was　considered　during　simulation,　the　results　indicate　the　peak　temperature　rise　4.8K　in　the　same　power(P　=　1W).　When　the　die　attach　exists　the　void,　the　temperature　distribution　of　IGBT　is　brought　more　changes,　the　surface　temperature　increase　24.9K　in　contrast　with　no　void　of　the　die　attach.