Based on the principle of laminated machining, the method of auto-programming in the electro discharge milling (ED-milling) process is drawn out.With the help of IGES formatted files, the process slicing and the machining locus can be programmed well.The program adopts three-parameter convergence as the basic way to slice the geometry mold and divide the non-uniform rational B-spline curve (NURBS) surface.With the great mount of discrete points, a given arithmetic is drawn out to order them, and then is carried out the interpolation of bi-arc.In the process, according to the character of the EDM process, the zigzag track of machining is accepted to remove the volume of work piece and shape the contour along the contour line of the slicing segments, including multi-connection.As a result, some correlative experiments are accomplished.