Abstract: Experiment of automobile crash indicates that the girder is the most important component to absorb the crash energy.Not only the size and material can affect ability of the girder to absorb the energy,but also the quality and the distributing of the welding spot have also important effect on the ability.A research on automobile girder by computer simulation is carried out in this paper.To take failure of the welding spot as the criterion,different interual and distribution method of welding spot are analyzed.Results indicate that the best way to avoid the failure of the welding spot is that the welding spot is in the balance place and the interval of welding spot is the half wavelengh of the distortion.A example is calculated by computer,and the results confirme the reliability and validity of this method.