Abstract: Non-quenched and tempered steel C38 + N for automobile can be used into not only crank shaft materials, but also produced engine connecting rods. By optimizing chemical composition (/% ：0.36 ~ 0.40C ,0.50 ~ 0.65Si, 1.40 ~ 1.55Mn,0.10 ~0.20Cr,0.015 ~0.020N,0.020 ~0.035S, ≤ 0.025P,0.003 ~0.015Al) and by feeding S wire to control sulfur content in steel etc, measures, the mechanical properties of steel C38 + N are Rp 0.2506 ~ 544 MPa Rm 854 ~ 879 MPa,A 12% ~23.5% and Z 26% - 30% to meet the requirement of standard.