The buffering characteristics of the coupled linear elastic cushioning packaging system for vulnerable parts are analyzed, and the influence of structural dimensions of EPE cushioning materials on the impact characteristics of packaging system considering vulnerable parts is studied based on the dynamic constitutive model of EPE cushioning material drop buffering. The method is to establish a nonlinear product packaging system dynamic model containing critical components, and use the least squares method to establish the relationship between the thickness and area of the EPE and the acceleration variation of the vulnerable parts. Based on the two principles that the response acceleration of vulnerable parts is less than the vulnerability degree and the amount of buffer material is the most economical, an optimized design mixed penalty function is constructed and the optimal solution is obtained. The results show that the thickness and area of the EPE buffer material have a significant impact on the acceleration of the vulnerable parts. The optimal value occurs under an optimized combination of a certain smaller liner area and an appropriate thickness, and the relative error of the relationship between the established EPE thickness and area is within 0.37%. This design method can effectively reduce the volume of buffer packaging and provide a way to verify the rationality of the structural dimensions of EPE buffer materials.