Cubic boron nitride (CBN) is synthesized by hexagonal boron nitride and catalyst under high temperature and high pressure. It is another new product that appeared after the advent of artificial diamond. Its hardness is second only to diamond, and its thermal stability is much higher than diamond. It has greater chemical inertness to Fe group metals. Therefore, CBN is unique in processing ferrous metal materials, providing a new means for processing such hard and tough difficult-to-process steels. Since diamond is suitable for processing hard and brittle materials, CBN can complement it. The grinding performance of cubic boron nitride abrasive tools is very excellent. It is not only capable of processing difficult-to-grind materials and improving productivity, but also effectively improving the grinding quality of workpieces. At present, the use of CBN is concentrated in two aspects, one is to manufacture abrasive tools, and the other is to make polycrystalline as tool materials.