By using the finite element met-hod, the simulation analysis and test verification on the tubes’ cross￣section deformation are carried out. It is pointed out that the change of tubes’ larger cross-section occurs nearby bending center corner and the change of smaller one takes place in tubes’ tangent segment. After the finite element calculation, there is large deviation in change-ratio of long axis on the cross-section, actual the reason is caused by the error of the match between tubes and dies.