The utility model relates to a gear milling clamp of a thin wall member. The gear milling clamp comprises a pedestal and a gear milling mandrel, and is characterized in that a double-end bolt is arranged on the pedestal, a spring and a pressure plate are arranged on the double-end bolt which is fixed on the pedestal through a hexagonal nut, the pressure plate comprises a pressure head, a connecting back with an adjusting screw and a support column, a positioning cylinder and an opening gasket are arranged on the gear milling mandrel, the positioning cylinder comprises a positioning end and a cylindrical shell, the external diameter of the positioning end is 8-12mm larger than the external diameter of the cylindrical shell, the external diameter of the positioning end is 0.04-0.1mm smaller than the internal diameter of the thin-wall outer spline of a part, and the gear milling mandrel is secured on the pedestal through an inner hexagonal screw. The gear milling clamp is simple in structure, easy for manufacture and convenient for mounting and dismounting parts. The thin wall outer spline end of a part is positioned in an auxiliary manner through the positioning cylinder, and the thin wall outer spline end of the part may not swing when the gear shaping machine shapes gears. Shaping gears are high in precision and stable in quality, and the qualified rate and the processing efficiency of shaping gears of the thin-wall outer spline of parts are improved. The production cost is reduced.