A novel enhancement-Type GaN HEMT with high power transmission capability using three-dimensional electron sea is proposed and investigated in this paper. After the calibration of the physics model with experiment data, the numerical simulation shows the proposed device features a very high on-state current of more than 3 A/mm. At the meantime, the breakdown voltage is not dramatically negatively influenced, rendering the proposed novel device has a potential in future power applications such as charging station, LED power manager, and wireless power transmission.