Abstract: In order to study the crashworthiness of the rear part of the car body and the main influencing factors when the car is rear-ended at high speed, based on the new FMVSS 301 regulations, the rear-end collision model is constructed jointly with HyperWorks and LS-DYNA software and simulation analysis is carried out at different impact angles, and the energy time characteristic curve of the extracted system is used to validate the accuracy of the model, and the analysis is carried out under the overlap rate of 70% of the rear-ended car and the impact velocity time characteristic curve of the door pillar, rear seat under the impact angle of 0°, 25° and 50°, respectively. The longitudinal deformation of the door column and the impact velocity of the rear seat are analyzed at 70% overlap rate and 0°, 25° and 50° impact angles, and the worst conditions are determined to be 0°−25°, respectively. Combined with the stiffness matching method, different parameters of the longitudinal beam thickness, rear bumper and rear bottom plate are set to change their stiffness in comparison with the parameters under the worst case, and the optimized model is simulated, and the maximum values of longitudinal deformation of the door column and the maximum value of the impact velocity of the rear seat after optimization are better than the original indexes. The crashworthiness of the optimized car body is improved. The results of the study can provide theoretical basis for the structural improvement of the whole vehicle.