The invention discloses a semi-fixed offshore wind turbine foundation. The semi-fixed offshore wind turbine foundation comprises a wind turbine, a tower drum, a floating drum, tensioning lines and a bottom semi-fixed foundation, wherein the wind turbine and the upper end of a sleeve are vertically arranged, the lower end of the sleeve and the upper end of the floating drum are vertically arranged, the tower drum and the floating drum are arranged on a straight line, the lower end of the floating drum and the bottom semi-fixed foundation are vertically arranged, one end of each of the plurality of tensioning lines is connected with the top of the floating drum, and the other ends of the plurality of tensioning lines are in uniform distribution connection with a seabed respectively by using the floating drum as the center. According to the semi-fixed offshore wind turbine foundation, the moving amplitude of the whole machine can be effectively reduced, so that the problems of difficulty in construction, high cost, instability and the like of a fixed foundation which is adopted in a transitional sea area are solved.