Abstract: Based on discrete element method-particle flow code,the equivalent rock mass representation model of granite is established,and the dynamic response of cutting force,micro-macro crack,debris generation,energy dissipation and other mechanism problems of cutting granite with PDC cutter under unidirectional stress and biaxial stress are studied.It is found that intragranular shear cracks and intergranular tensile cracks are two main crack types generated during rock cutting process.The number of cracks increases with the increase of cutting depth.Under unidirectional stress,both confining pressure and hydraulic pressure will compact the rock,reduce the number of cracks and increase cutting energy consumption,Moreover,the influence of hydraulic pressure on granite crushing is higher than that of confining pressure at the same value,while large confining pressure or hydraulic pressure will increase the number of intergranular tensile cracks.Under biaxial stress,the influence of hydraulic pressure on granite breakage is much higher than that of confining pressure at the same value,and the relative magnitude of confining pressure and hydraulic pressure is an important factor affecting the crushing of granite.The research results can provide reference and basis for drilling speed-up in deep hard and brittle granite formations.