Abstract Under vertical impact loads, such as explosions, serious compressive deformation occurs in the pelvic bones and lumbar vertebrae of the human body leading to injuries or fatalities for occupants. This study focuses on the occupant-seat model in military vehicles, establishes a biomechanical model of the human spine, and establishes the relationship between vertical impact loads and human injuries. Subsequently, a C-shaped energy-absorbing cushioning structure is designed for application at the bottom support of the seat. Using a peak value of 50 g explosion-simulated triangular wave loading, the study compares the attenuation effects of different structural characteristics of cushioning energy-absorbing structures on impact loads. The results indicate that a 50 g peak vertical impact load can cause significant human injuries. The designed energy-absorbing cushioning structure can greatly reduce human response, but both excessively soft and rigid energy-absorbing cushioning structures fail to achieve effective impact attenuation.