The invention discloses a III-V group MOS (Metal-oxide Semiconductor) field effect transistor with high mobility, which comprises a single-crystal lining, a buffer layer formed on the single-crystal lining, a planar doped layer formed in the buffer layer, a high-mobility channel layer formed on the buffer layer, a doped interface control layer formed on the high-mobility channel layer, a high-doped semiconductor layer formed on the doped interface control layer, a narrow band gap ohm contact layer formed on the high-doped semiconductor layer, and a source-drain metal electrode formed on the narrow band gap ohm contact layer, wherein a grid groove etched to the doped interface control layer is located between two source drain metal electrodes; a high-K grid medium is uniformly covered on the inner surface of the grid groove structure; and a grid metal electrode is formed on the high-K grid medium. The III-V MOS device structure disclosed by the invention not only can lower MOS interface state density, and improve channel mobility, but also can improve channel two-dimensional electron (cavity) gas concentration, and satisfy the application demand of a high-speed lower voltage operation high mobility CMOS technology.