The invention provides an enhanced type HEMT (high electron mobility transistor) device based on an AlGaN/GaN (aluminium gallium nitride/ gallium nitride) heterojunction of a Si (silicon) substrate, and a manufacturing method thereof. The enhanced type HEMT device comprises an Si substrate (101), an AlN (aluminum nitride) nucleating layer (102), AlGaN transition layers (103-105), an AlGaN buffer layer (106), a low-temperature AlN inserting layer (107), an AlGaN main buffer layer (108), an AlGaN/GaN superlattice layer (109), a GaN channel layer (110) and an AlGaN barrier function layer (111), wherein a source electrode (112) and a drain electrode (113) are arranged at both sides of the top end; a grid electrode (116) is arranged in the middle part of the top end; the middle AlGaN barrier function layer (111) is etched into a groove, and the bottom part of the groove is in contact with the GaN channel layer (110); a passivating protecting layer (114) and a grid medium layer (115) are deposited to the bottom part of the groove; the grid electrode (116) is arranged on the medium layer. The enhanced type HEMT device has the characteristics that the high threshold voltage, high breakthrough voltage, high current density, and excellent pinch-off characteristics are realized; the manufacturing technology is simple, the repeatability is good, and the enhanced type HEMT device is applied into high-voltage and high-power electronic devices.