In the process of hard cutting die steel Cr12MoV，the workpiece material hardness is very high，sothe tool endure severely thermo mechanical coupling effects. Tool wear mechanism is different from the traditionalcutting process. Based on the PCBN tool precision cutting process of die steel Cr12MoV，in this paper the tool rakeface wear and the flank face wear form are studied，and tool wear mechanisms in different positions through ele-menu change analysis is researched. Under different cutting speeds and feeds tool wear research regularity resultsprovide theoretical basis for reasonable selection of cutting conditions. The research results reveal that cutting forceis affected by mechanism of cutting tool wear. Different tool wear amount of geometric model are founded by usingUG software. different cutting EEM models are founded to research effect of tool wear on cutting temperature by using Deform software in this paper.