To solve the aerodynamic effects of road tunnel caused by high-speed trains passing through tunnels, this paper proposes a new type of discontinuous buffer structure. In the current research on buffer structures, no research has been conducted on the length ratio of buffer sections and the discontinuous buffer structure. Based on the ^κ-ε two-equation turbulence model, the dynamic mesh technology provided by Ansys Fluent software is used to simulate the entire process of high-speed trains passing through buffer structures and tunnels at a speed of 350 km/h. By optimizing variables such as the discontinuity distance a of the buffer structure, the length L_i of each buffer section, the cross-sectional area A_i, and the number of buffer sections n, a discontinuous buffer structure that can effectively mitigate pressure gradient peaks is designed. The calculation results show that when these variables are set as a=0.50 m, L₁∶L₂∶L₃=1∶1∶1, A₁=A₂=A₃=150 m² and n=3, the pressure gradient reduction effect is the best, reaching 44.04%.