Abstract: To address the issues of high falling block risk at the vault and low construction efficiency in traditional initial support technologies for super-large cross-section tunnels under complex geological conditions, this study investigates the Steel Corrugated Plate-Steel Frame Composite Initial Support Structure. Through numerical simulations and model tests, the mechanical characteristics and engineering applicability of the structure were examined to validate its safety, deformation control capability, and synergistic bearing mechanism under complex geological conditions. The results showed that: (1) During excavation and support, the composite structure exhibited comparable performance to traditional shotcrete-bolt support in terms of surrounding rock deformation control and structural stress-deformation behavior. (2) The failure threshold of the composite structure was significantly higher than that of traditional shotcrete-bolt support, with smaller crack propagation ranges. Its deformation and stress states during loading were notably superior, demonstrating enhanced structural integrity. (3) The corrugated plate exhibited distinct stress mechanisms at its peaks and valleys: compressive stress dominated at the peaks, while tensile stress dominated at the valleys. (4) The corrugated plate primarily sustains tensile axial forces. During loading, the axial force at the vault gradually increases to a tensile peak, then decreases, and ultimately transitions to a compressive state, with this trend propagating toward both sides during loading. The findings demonstrate that the Steel Corrugated Plate-Steel Frame Composite Initial Support achieves comparable support capacity and superior failure resistance to traditional shotcrete-bolt support through its synergistic bearing mechanism. This solution effectively mitigates vault falling block risks, improves assembly rates to accelerate construction progress, and is applicable to soft rock masses, fractured zones, and rockburst-prone strata.