The service life of dies can been improved significantly by the machining process of “cutting in place of grinding” which the mold working part be highly processed with super hard cutters. But there are few studies on it. The tool wear was observed, detected and analyzed by thermometer, optical instrument, tool microscope (XGJ-1) and SEM (JSM-5600LV) when high speed machining hardened AISIH13(HRC53) with super hard cutting tool PCBN. The result shows it is mainly adhesive wear in the rake face and flank surface, but the cutting heat is primary cause of rake wear, while the mechanical stress is dominating reason, and groove wear often lies on the cutting edge of the main cutting edge, also irregular breakage can been generated when the cutting is not balanced.