In this study, analysis on the stiffness of the headrest, the stiffness of front-rear load and the torsion of cushion frame was performed using finite element method in order to investigate the properties of the stress-deformation by material characteristics according to the test requirements of FMVSS (Federal Motor Vehicle Safety Standard). The results are shown that AZ31 (Mg alloy) and A365 (Al alloy) with low modulus of elasticity and density have higher strain rate than steel in terms of stress-deformation and meet the standards for safety within 108 mm of the maximum amount of deformation. Considering it’s safety and durability, however, the selection of AZ31 for light weight seems difficult to gain the reliability because it causes an excessive deformation, and therefore it is not expected to be used for recliner where stress is concentrated and also the bracket linking rail and cushion frame.