Since frontal collision is the dominant form of automobile accidents, there have been many researches on the occupant behavior during the frontal collision. Most of these researches use complicated dynamics models of the multiple degrees of freedom and large-scale FEM. Therefore, it is difficult to make use of them for the initial design because the specifications of body structures and protection devices are not determined in the initial stage. In this paper, a simplified occupant model with small degrees of freedom was introduced, and the spring characteristics of each body joint and the seat belt were identified by experiments with sled testing. As a result, a prediction of the chest deceleration, which is one of the most important performance indexes, and an analysis of the dynamics mechanism at the initial design stage became possible.