To analyze the rear end crash of a motor vehicle using a beam-element model, it is important how to model the upper body panel members such as rear doors or rear quarters. This paper describes the method of modeling each panel member into a beam element considering the “effective areas” in each member section. The panel member is cut into several sections along its longitudinal axis. Applying the thin-shell buckling theory and experimental analysis to each section, “effective areas”, which withstand up to the yield stress when the panel member is subjected to longitudinal compression, can be selected. With the section characteristics of the “effective areas”, a beam element for the panel member is defined. The results of the calculation by this method showed a good correlation to the experimental results of three kinds motor vehicles with the body deformation mode or crash length etc.