This paper is concerned with the energy absorption efficiency of an auto-body side structure when it is fabricated with the conventional steel or the 60TRIP high strength steel. The energy absorption efficiency has been estimated with the dynamic crash analysis following the regulation of US-SINCAP. The analysis adopted the Johnson-Cook model for the dynamic material properties in order to achieve accurate crashworthiness assessment. The dynamic material properties were obtained from the dynamic material test with a tension split Hopkinson pressure bar test. The analysis result provided deformed shapes, amounts of penetration and accelerations at several important points during auto-body side crash. It is noted from the result that the use of the 60TRIP steel greatly improves the crashworthiness of the side members without sacrificing the weight and thus can be used for the light-weight design of an auto-body.