The deforming situation of seamless steel tube in the tension reducing process was simulated by means of a large-scale and common finite-element analysis software ANSYS/LS-DYNA,this simulation could present the deforming situation objectively.The simulated distribution of the stress and the strain could well explain the phenomenon of unequal wall thickness in the tension reducing process.The simulation process for deforming is almost the same as the practical once.This research conclusing could be used for analyzing,establishing and optimizing the technological system in the steel tube reducing process.