The invention discloses a common positioning fixture for a CNC milling machine, and mainly relates to the field of mechanical manufacturing. The common positioning fixture comprises a base, a cavity is arranged at the bottom of the base, a lead screw is arranged at the middle portion of the interior of the cavity, a spline shaft is arranged at the end, extending out of the base, of the lead screw,the two sides of the lead screw are provided with inclined supporting rods, sliding blocks are arranged on the inclined supporting rods, a nut is arranged on the lead screw, guide rods are arranged on the two sides of the nut, the sliding blocks are provided with penetration holes matched with the guide rods, a vertical plate is vertically arranged on the tops of the sliding blocks, a clamping block is arranged on the side, close to the lead screw, of the vertical plate, T-shaped sliding blocks are symmetrically arranged at the bottom of the clamping block, the bottom faces of the T-shaped sliding blocks and the top faces of the sliding blocks are located on one horizontal face, and a positioning block is arranged at the end between the two clamping blocks. The common positioning fixturehas the beneficial effects that workpiece clamping and positioning can be quickly completed, the tool setting time number can be reduced, workpiece extrusion is avoided, the machining quality is guaranteed, and the working efficiency is improved.