Subdrilled cut blasting technology is extensively employed for deep shaft sinking through hard rock formations. In contrast to equal-depth cutting methods, where the cutting depth matches the auxiliary hole depth, this advanced technique significantly improves advance per round and enhances blast hole utilization rate. Optimizing subdrilled-cut parameters is of substantial engineering significance in hard-rock shaft-sinking projects. Based on the actual blasting design and geological conditions at the auxiliary shaft of the Ansteel Group Iron Mine in Xi′anshan, this study uses the numerical simulation software ANSYS/AUTODYN to establish 7 types of subdrilled cut-blasting calculation models, including cutting holes and auxiliary holes. Through comprehensive simulations of excavation blasting processes under varying subdrilling configurations, the research systematically analyzes variations in rock particle velocity and overpressure dynamics during detonation. These investigations aim to elucidate the mechanisms of damage evolution in rock masses under different subdrilling conditions and to determine the optimal depth range for maximum blasting efficiency. Results demonstrate that subdrilled cut blasting substantially enhances advance performance compared to traditional methods. Both peak rock pressure and particle ejection velocity between the cutting and auxiliary holes increase progressively with greater subdrilling, thereby promoting rock fragmentation and excavation efficiency. However, this growth trend gradually stabilizes as subdrilling increases. Field validation confirms significant tunnelling improvement after parameter optimization, achieving an average advance per round of 4120 mm (with a 4500 mm perimeter hole depth and a 500 mm subdrilling) and a monthly progress exceeding 115 m. These findings provide valuable references for optimizing subdrilling parameters in similar engineering projects.