Shield tunneling through high-speed railway infrastructure projects is becoming increasingly frequent, but the research on the laws of deformation caused by shield tunneling through high-speed railway infrastructure projects is still rare and unsystematic. The zoning of the impact of shield tunneling on high-speed railway infrastructure is also lacking in more detailed, mature, and practical results. Based on the case study of underpass high-speed railway subgrade and tunnel, this paper uses numerical simulation to carry out systematic parameter research, combined with orthogonal tests and single factor variable analysis, to study the impact law and impact area zoning of shield tunneling underpass high-speed railway infrastructure engineering. The study suggests that when designing the underpass angle, the impact of horizontal irregularities on the main impact area should be fully considered, and the angle should preferably be controlled above 40 °. As the clear distance between the shield and the tunnel to be penetrated increases, the scope of influence gradually expands, and the maximum settlement, track height irregularities, and horizontal irregularities gradually decrease. As the stratum becomes weaker and weaker, the maximum settlement gradually increases, and the impact scope gradually expands. For high-speed railway tunnels and subgrades with different stratum conditions, reasonable clear distance between shield and high-speed railway infrastructure is proposed. In order to facilitate the judgment of the impact scope of shield tunneling on high-speed railway in engineering, based on a large number of simulation results, the impact area division of seven strata under five burial depths is proposed by merging similar soil layers and burial depths, which can provide reference for shield tunneling on high-speed railway projects.