Electrical determination of the channel temperature used for AlGaN/GaN high-electron-mobility transistors (HEMTs) is proposed. The measurement is based on the pulse technique that superposes a detecting pulse on the quiescent bias to acquire the electrical response under various thermal conditions.Practical experiments and electro-thermal simulations manifest that the duration of the pulse used has a fairly slight influence in the measured results.Finally,noticeable variance of thermal resistance at different gate biases is reported and the thermal resistance as a function of gate voltage decreases from 18.6 to 12.3℃.mm/W as the gate bias increases from -1 V to 2 V under low power density condition.