In　this　study,　the　maximum　spatial　resolution　of　infrared　thermal　imager　is　3　μm,　and　the　gate　length　of　AlGaN/GaN　HEMTs　is　between　0.2　μm　and　1　μm.　Therefore,　the　infrared　thermal　imaging　instrument　measurement　results　are　only　an　average　temperature　that　is　lower　than　the　actual　temperature.　By　combining　infrared　thermal　imaging　with　Sentaurus　TCAD　simulation,　the　junction　temperature　of　AlGaN/GaN　HEMTs　can　be　accurately　measured.　First,　with　the　infrared　thermal　imager　under　different　loading　power　settings　and　the　shell　temperature　of　the　AlGaN/GaN　HEMT　junction　temperature　increase,　the　Sentaurus　TCAD　of　AlGaN/GaN　HEMTs　for　steady-state　and　transient　simulations　is　measured.　Then,　the　use　of　the　infrared　thermal　imager　is　measured　under　different　power　settings　of　AlGaN/GaN　HEMTs　active　region　temperature　as　the　boundary　condition　to　optimize　parameter　model.　Then,　the　junction　temperature　of　the　AlGaN/GaN　HEMTs　is　extracted　from　the　model,　which　has　a　resolution　of　0.05　μm　-2　μm.　©　2017　IEEE.