Temperature-dependent electrical behavior and trap effect in AlGaN/GaN high-electron mobility transistors (HEMT) were investigated at temperatures ranging from 25 ℃ to 125 ℃. The experiment results show that transfer curves negatively shift and transconductance degrades with the increase in temperature at DC and pulsed conditions, meanwhile, gate leakage current increases significantly. Besides, the shift variation of pulsed transfer curves becomes larger at the elevated temperature and static bias states. This mechanism could be attributed to the enhancement of electron-assisted tunneling ability and easily escaping from the traps for trapped electrons at higher temperature. These traps were confirmed on the base of low frequency noise technique under different temperatures, and the extracted activation energy is 0.521 eV for the present devices. The above results may provide useful guidance for design and application of the AlGaN/GaN HEMT.