Molds used for injection molding usually go through two main steps, one of which is CNC processing and the other is EDM machine Processing. The use of CNC processing accuracy alone is not sufficient for injection molding. But using EDM machines can meet the need. Firstly, EDM machines are virtually unaffected by heat in the process, thus reducing the heat-affected layer and the high quality of the machined part. Secondly, in the low-speed wire is constantly updated, which is conducive to improving the processing accuracy and reducing surface roughness. Then it can cut a narrow slit of about 0.05mm and the cutting efficiency that EDM wire cutting can achieve is generally 20~60mm 2/min, up to 300mm 2/min; the processing accuracy is generally ±0.01～±0.02 mm, up to ±0.004 mm; the surface roughness is generally R2.5～1.25 micron, up to Rα0.63 micron; the cutting thickness is generally 40~60mm, the thickest can reach 600mm. Finally, EDM processing can achieve the vertical corner of the workpiece; this is the milling process can not be achieved because the milling process is bound to have the R angle exists.