The invention discloses a metal oxide semiconductor field effect transistor power device with a bottom gate, which comprises a first conductive substrate, a first conductive epitaxial layer and multiple device trenches, wherein the first conductive epitaxial layer is located on the first conductive substrate; and the multiple device trenches are arranged on the upper surface of the first conductive epitaxial layer, a bottom gate, a separation gate and a trench gate arranged from deep to shallow are arranged in each device trench, a bottom insulation layer is arranged between the bottom gate and the first conductive epitaxial layer, a middle insulation layer is arranged between the bottom gate and the separation gate, and an upper insulation layer is arranged between the separation gate and the trench gate.