Abstract: PCBN composites was used as the tool material, its related mechanical properties were analyzed. Then, it was made into SNGN120408 type tool and the hardened steel cutting experiment was carried out on the tool machine. The analysis results show that the binders of the PCBN composites are mainly TiN and TiB₂. The internal structure is evenly distributed and has good compactness. Cutting experiments show that in the hard cutting process, the cutting speed and cutting feed rate have a more obvious impact on tool wear than the cutting depth. Compared with cutting speed, the feed rate has a greater influence on the surface roughness of hardened steel workpiece. The wear of PCBN tool high-speed cutting hardened steel is the result of multiple wear such as bond wear, local spalling and diffusion wear.