Abstract: The lack of clarity over the rock breaking mechanism of triangular prismatic cutters hinders their effective applications. In view of this, the finite element method was employed to conduct a numerical simulation analysis of triangular prismatic cutters in this study with the aim of clarifying the change rules of various cutter force during rock breaking and revealing the rock breaking mechanism. The results of numerical simulation and scraping experiments suggested that triangular prismatic cutters and planar PDC (polycrystalline diamond compact) cutters demonstrated a distinct difference in the stress on the rocks during breaking. The tangential force and its fluctuation were smaller when a triangular prismatic cutter was used to break sandstone as compared with a conventional planar cutter under the same conditions. The field test of the PDC bit with the triangular prismatic cutters proved a high efficiency in rock breaking and impact resistance in strata with high abrasiveness and strong impact. This study demonstrates that breaking rocks using tension and shear, triangular prismatic cutters can make the tangential force and torque smaller and the impact resistance and abrasion resistance higher. In that way they can enhance the rock breaking efficiency and prolong the service life of bits.