The invention discloses a metal-insulator-semiconductor (MIS) grid enhanced high electron mobility transistor (HEMT) device based on gallium nitride (GaN) and a manufacture method of the MIS grid enhanced HEMT device and mainly solves the problems that the current density and the reliability of the existing GaN base enhanced device are low. The device is structurally characterized in that a transition layer (2) and a GaN main buffer layer (3) are sequentially arranged on a substrate (1), the middle of the GaN main buffer layer (3) is provided with a groove (11), an AlGaN main barrier layer (4) is arranged above the GaN main buffer layer arranged at two sides of the groove, a GaN sub buffer layer (5) and an AlGaN sub barrier layer (6) are sequentially arranged on the surface of the AlGaN main barrier layer (4) arranged above the groove inner wall and the two sides of the groove, the two sides of the top end of the AlGaN sub barrier layer (6) are respectively a source electrode (8) and a drain electrode (9), a medium layer (7) is arranged outside the source electrode and the drain electrode, a grid electrode (10) is arranged on the medium layer (7) and covers the whole groove region, and the mature flow process is adopted for the whole device manufacture. The MIS grid enhanced HEMT device has the advantages that the enhanced type characteristics are good, the current density is high, the breakdown voltage is high, and the device reliability is high. The MIS grid enhanced HEMT device can be used in high-temperature high-frequency high-power devices, high-power switches and digital circuits.