Abstract: Aiming at the crew safety problem in the environment of explosion and shock at the bottom of vehicle, this paper combines the experimental research with finite element simulation to study the movement and damage of the crew's lower limbs in the explosion and shock environment. A honeycomb aluminum lightning protection foot pad is designed as the protection device of the crew's lower limbs. The protective performance of the foot pad is studied in the explosion and shock environment, the influence of different gradient structures on the response of lower limbs of the crews in the vehicle is studied, the multi-objective optimization design of the honeycomb aluminum lightning protection foot pad is carried out, and the thickness-gradient honeycomb aluminum lightning protection foot pad is obtained. The results show that the honeycomb aluminum lightning protection foot pad designed in this paper can effectively reduce the lower tibia force and the injury of lower limbs of the crew by absorbing energy and reducing the impact strength, the gradient structure has better energy absorption characteristics than the homogeneous structure, different gradient structures have different protection effects on lower limbs of the crew, and the thickness-gradient has the greatest impact on the response of lower limbs of the crew. Compared with the original model, the optimized crew lower limbs protection device can reduce the left lower tibia force by 26.35%, the right lower tibia force by 24.69% and the total mass of the foot pad by 56.59%.