Abstract: Hole processing is a common machining process in the field of mechanical processing, while ladder hole processing occupies an important position and has a wide range of application. Automobile brake pads material is wear-resistant material, ordinary hard alloy cutting tool is easy to wear out. Its production efficiency is low and production cost is high. Diamond coating tools often have good machinability when drilling such materials. By using hot wire CVD diamond researched by Shanghai Jiao Tong University, aiming at the diamond coating technology of the special tool for ladder hole processing, the preparation device is researched.