In order to process the hardened face-gear, the worm for face-gear is studied. The research includes designing and dressing method of worm. According to the meshing relationship of face-gear, worm and shaper, coordinate systems of face-gear, worm and shaper are established. By envelope theory, the face-gear tooth surface are obtained, worm tooth surface and shaper tooth surface. The solid models of face-gear, worm and shaper were built, and the approach of dressing was simulated for hardened face-gear processed.