Abstract: This study focuses on the bulge-type energy-absorbing structure used in rail vehicles. Numerical simulations were conducted to investigate the influence of key structural parameters—namely, wall thickness, inner diameter, and length—on the crashworthiness of the energy-absorbing tube. The results indicate that wall thickness and inner diameter are the dominant factors determining crashworthiness performance. The average crushing force increases with wall thickness but decreases as the inner diameter increases. For a given crushing displacement, the total energy absorption capacity increases with wall thickness. In contrast, the tube length has a negligible impact on crashworthiness. The findings provide a theoretical basis for the optimal design of high-performance energy-absorbing structures and are of significant engineering value for enhancing occupant protection and the structural integrity of the car body during train collision events.