The　effects　of　self-heating　and　traps　on　the　drain　current　transient　responses　of　AlGaN/GaN　HEMTs　are　studied　by　2D　numerical　simulation.　The　variation　of　the　drain　current　simulated　by　the　drain　turn-on　pulses　has　been　analyzed.　Our　results　show　that　temperature　is　the　main　factor　for　the　drain　current　lag.　The　time　that　the　drain　current　takes　to　reach　a　steady　state　depends　on　the　thermal　time　constant,　which　is　80　μs　in　this　case.　The　dynamics　of　the　trapping　of　electron　and　channel　electron　density　under　drain　turn-on　pulse　voltage　are　discussed　in　detail,　which　indicates　that　the　accepter　traps　in　the　buffer　are　the　major　reason　for　the　current　collapse　when　the　electric　field　significantly　changes.　The　channel　electron　density　has　been　shown　to　increase　as　the　channel　temperature　rises.　©　2014　Chinese　Institute　of　Electronics.