In order to explore the rock breaking law of conical cutterhead for large-diameter vertical shaft boring machine with pilot hole, the rock breaking simulation model of cutter in conical cutterhead was established using discrete element method. The rock breaking characteristics of the cutter in the near and far face is studied, and the influences of cone angle, distance from the free face and space between cutters on the rock breaking state, cork crack propagation and the energy consumption ratio are deeply analyzed. The correctness of the simulation model is verified by cutter breaking conical rock. The results show that: The cone angle of cutterhead, distance from the free face and space between cutters have significant influence on the rock breaking. The optimal cutter spacing of near face and far face decreases with the increase of cone angle. Furthermore, the rock breaking efficiency of cutter in near face is higher than that of cutter in far face. The research results can provide reference for conical cutterhead design and cutter layout for vertical shaft boring machine.