Topics such as passengers safety, seat performance in the crashes, energy absorption by the seat, are the major concern in vehicle design. Automobile seat, as a member which is in direct interaction with the passenger, has a major rule in providing passengers safety. Statistics show that rear-side collisions, which cause severe injuries, have the forth rank among other type of crashes. Moreover, three out of four injuries caused by such crashes, are neck injuries. Therefore, seat design has a major rule in reducing the severity of the neck injuries. In this study, the measurement of the energy index by using FEM based method has been introduced, and the technique to increase the energy absorption by the seat structure has been investigated, and the effect of design parameter-variation on the severity of injuries has been studied via the simulation of rear-side collision. In this article most important patents are also discussed.