Abstract: The average crushing force determines the energy absorption capacity of the longitudinal beam in a passenger vehicle during the collision process. The longitudinal beam is usually in the form of rectangular thin-walled beam because of its high collapse and shrinkage energy absorption ratio. In this paper, the axial crushing experiment was carried out to study the crushing performance of rectangular thin-walled beams. The formula of the average crushing force of rectangular thin-walled beams was deduced by using the asymmetric super-folding element theory. The finite element numerical simulation of rectangular thin-walled beams was carried out to obtain the experimental, theoretical and simulated values of the average crushing force. By comparing the these results, it was concluded that the theoretical and numerical results of the average crushing force were consistent with the experimental results, which provided an effective theoretical guidance for the early structural design of rectangular thin-walled beams.