Motor vehicle industry uses high surface quality SAE 9254 spring steel to manufacture suspension springs.By means of DMAIC method and process tracking associated with ANOVA and SAS Statistics, we identified that billet surface grinding roughness, reheating temperature, and soaking time are three main factors causing sliver of rod surface defects. We adopted (1) bloom scarfing to reduce the excessive grinding of the surface defect; (2) fine-grained grinding with low pressure to optimize the billet grinding operation; and (3) proper reheating temperature and soaking time of the billet to minimize the sliver of residual grinding marks.With the improvements, the acceptance ratio of rod surface quality increases from 79% to 96% while the defect ratio of spring surface pits decreases from 10% to 0.19%.