A study was conducted to address the issues of rapid damage and low rock-breaking efficiency of polycrystalline diamond compact (PDC) bits in hard formations and heterogeneous interbedded formations. Through single-cutter rock-breaking experiments and finite element simulations, a heterogeneous conglomerate model was established using INP file secondary development. The rock-breaking process under varying back rake angles, cutting depths, and trajectories was simulated, with analyses focusing on rock fragmentation patterns, stress distribution, and load characteristics. The mechanisms influencing rock-breaking performance were revealed. The results show that planar cutters exhibit a positive correlation between cutting efficiency and back rake angle, achieving maximum efficiency at 30°. In contrast, axe-shaped cutters show peak efficiency at 20° with a nonlinear relationship to back rake angle, accompany by reduced cutting ranges as angles increase. At a cutting depth of 10 mm, stress values increase significantly, stress-affected zones expand, and rock deformation intensifies, yielding the minimum specific rock-breaking energy of 5.41 mJ/mm³. The ridge-like protrusion at the front of axe-shaped cutters initially contacts the rock, forming localized stress concentration zones that facilitate efficient fragmentation. Additionally, stress fluctuations during cutting trajectories remain stable. By optimizing back rake angles and cutting depths, rock-breaking efficiency is maximized. The research results provide critical theoretical guidance for the customized design of PDC bits, particularly for drilling in conglomerate layers and heterogeneous formations.