In this article, a dynamic charge storage mechanism is proposed for designing the p-GaN gate dynamic charge storage high-electron-mobility transistor (DCS-HEMT) with ultralow switching loss. The device features a p-doped DCS layer in AlGaN buffer. When the DCS-HEMT is turning off, the net negative charges in the DCS layer significantly contribute to the depletion of 2-D-electron-gas (2DEG) channel, leading to low turn-off loss ( $E _OFF$ ). During turn-on process, reduction of the negative charges amount could accelerate the formation of electrons at the 2DEG channel, which results in low turn-on loss ( $E _ON$ ). Verified by the calibrated simulation, total switching loss ( $E _text SW boldsymbol = E_OFF +E_ON$ ) of the designed DCS-HEMT is 61% lower than that of the conventional p-GaN gate HEMT (C-HEMT). The improved performance makes the DCS-HEMT a competitive candidate for low switching loss power applications.