A high-precision and efficient machining method of plane double enveloping hourglass worm is proposed. The worm tooth surface is first created and analyzed based on meshing theory. The analysis reveals that the worm tooth surface is a developable ruled surface. This provides the ability of precise flank milling of the worm tooth surface. The meshing lines on the worm tooth surface indicate the contact lines of the worm tooth and the cutter. The five-axis tool path of flank milling is then generated according to the meshing lines. The flank milling has obviously advantages in machining efficiency and surface quality, compared with the conventional end milling method. The cutting simulation and experiment validate proposed method.