In this study, the design and optimization of a honeycomb energy absorber is performed using genetic algorithm. The main design goal is to absorb almost whole impact energy. Simultaneously, the reducing of the shock force level is also considered as a main objective. In the first part, the crashworthiness behavior of honeycomb structure is parametrically studied. The results are utilized in the second part to optimize shock absorber design. In this part, aluminum honeycomb structure under dynamic loading is investigated using simulation in LS-dyna finite element code. Parametric studies are invoked to identify the influence of different model parameters on crashworthiness characteristics of honeycomb structure. Reducing the computational cost, a repeatable model of 'Y' cross section column is numerically simulated. The effects of changes in material properties including Young's modulus, yield stress, tangent modulus, geometrical properties such as cell size, foil thickness, as well as the effects of impact velocity on the deformation behavior of the structure were investigated. A number of 25 different geometries with same height and various cell sizes and thicknesses are studied and effects of thickness and cell size on the energy absorption properties is investigated. Results showed that crashworthiness parameters such as mean and peak stress depend mainly on cell size and thickness values, while the friction coefficient and young's modulus are of less importance. Any change in absorber’s geometry affects the mean collapse stress more severe than the peak stress. In the meantime, thickness change is more effective in comparison with cell size change.