Abstract: The purpose of this paper is to determine the structural design method for tunnels undercrossing the air? port terminal section in high-speed railway throat area under a complex environment. Based on the tunnel project undercrossing the GTC and the T2 terminal of the Yaoqiang International Airport, which is on the Jinan connection line of the Tianjin-Weifang High Speed Railway, the structural form, structural stress, pile foundation layout, tunnel settlement and deformation control and structural strengthening measures for the tunnel are studied, so as to propose the straight wall, flat top and circular arch structure form, the long-span straight wall tie-arch structure form, the uniform layout pattern of pile foundation and the structural measures of the overall vertical and horizontal hidden beams plus locally reinforced ring beams, and to analyze the above-mentioned structural forms. The results show that the use of straight wall, flat top and circular arch structure and the large span straight wall tie-arch structure in the undercrossing tunnel can meet the load-bearing requirements. The deviation between the two-dimensional calculation result of complex cross-section tunnel structures and the three-dimensional calculation result is only 14%. During design, reinforcement can be made based on the two-dimensional calculation result and verified based on the three-dimensional calculation result. The uniform layout scheme of pile foundation is more beneficial to controlling deformation and settlement of the tunnel structure, and the measures of setting vertical and horizontal hidden beams can improve rigidity and stability of the tunnel structure.