In　this　study,　we　investigated　the　effects　of　temperature　and　bias　voltage　on　the　electron　transport　properties　of　AlGaN/GaN　high-electron-mobility　transistors　in　the　saturation　region　using　a　turn-on　delay　time.　A　sine　wave　signal　was　used　to　accurately　acquire　the　delay　time　between　the　gate-source　voltage　and　drain-source　current　signal　of　the　device　at　temperatures　ranging　from　30　degrees　C　to　180　degrees　C　under　operating　conditions.　With　this　method,　we　illustrated　a　non-monotonic　relationship　between　the　temperature　and　the　delay　time,　which　was　closely　related　to　the　effect　of　temperature　on　saturation　drift　velocity　and　charge　trapping.　In　addition,　it　suggested　that　the　delay　time　increased　with　increasing　drain-source　voltage,　which　was　ascribed　to　the　effect　of　charge　trapping.　The　validity　of　the　proposed　results　has　been　thoroughly　verified　with　similar　phenomena　on　two　samples.　The　results　may　be　useful　for　further　study　on　the　electron　transport　of　GaN　HEMTs　under　high　temperature　and　voltages.