Problems about rock cutting are often encountered in the fields of oil drilling and tunnel excavation. The research of rock cutting problems has become an important breakthrough to improve the efficiency of mechanical mining. Aiming at the scientific problem of plastic-brittle fracture mechanism of rock cut by conical teeth during drilling， the numerical simulation of parallel rock cut by conical teeth was established through experimental testing of rock mechanics parameters and discrete element method （PFC2D） to study the cutting morphology， cutting force and rock break specific energy of rock cut at different cutting depths during rock cutting. The results show that： （1） the macro-shear crack is first generated in the cuttings to form semi-shedding cuttings， and then the tensioning failure occurs in the weak area to cause the cuttings to pop out， and the small size cuttings are generated when the cutting depth is shallow， and the large size cuttings are generated when the cutting depth is deep. （2） The peak cutting force that generates rock chips at different cutting depths was studied and found to be better in agreement with Nishimatsu’s peak force model， showing a linear increase trend with cutting depth. （3） The peak value of cutting force corresponds to the surge of cracks， and the number of steps in the crack chart will decrease with the increase of cutting depth. The specific energy of rock breaking is positively correlated with the cutting depth in a certain range， and the cutting process can be divided into plastic ductile stage， fragmentation stage and brittle failure stage according to the relationship diagram of and .