Abstract: By using ANSYS finite element software,the strength and rigidity parameters of a longitudinal beam for heavy truck before and after material improving had been calculated when elastic bending or warping happened,and these two calculated results had been contrasted and analyzed. The results show that the ‘7+4’ longitudinal beam made of P590L material had higher strength than the ‘8+5’ longitudinal beam made of P510L material. Rigidity of the improved longitudinal beam decreased a little,but it still could meet with the design requirement.