In this study, the current-transient method has been conducted to investigate the trap states in p-GaN gate high-electron-mobility transistors (HEMTs) under reverse gate stress. An irregular threshold voltage shift under reverse gate bias has been observed through the pulsed transfer measurements with different delay times. It suggests that both the hole insufficiency and hole trapping are generated during the reverse gate pulse bias. With proper selection of the delay time based on the pulsed characterizations, the hole detrapping can be effectively evaluated after the hole recovery is completed. In addition, by subtracting the trapping behavior caused by the measurement condition, the actual detrapping transient under reverse gate filling voltages can be obtained with the current-transient method. Three traps have been observed with the energy levels of 0.484, 0.390, and 0.235 eV. The identification of hole traps may provide a basis on the understanding of threshold voltage instability and further improvement of the reliability of p-GaN gate HEMTs.