The dressing regime parameters in the process of grinding are the most important enabling factors that need to be determined. In this study, the influence of dressing regime parameters (the rough dressing depth, the dressing feed rate, the fine dressing depth, rough dressing times, fine dressing times, none-feeding dressing times) on roundness tolerance for external grinding of SKD11 steel is introduced. The Taguchi technique in designing the experiment and analyzing of variance (ANOVA) have been applied to define the influence of dressing regime parameters on the roundness tolerance. The results show that the impact level of fine dressing times (nf), none-feeding dressing times (n0), fine dressing depth (af), rough dressing times (nr), rough dressing depth (ar), dressing feed rate (Sd), and errors on roundness tolerance (Rt) are 62.88%, 19.70%, 9.85%, 3.79%, 1.52%, 1.52% and 0.76% respectively. Finally, by analyzing experimental results, optimized dressing parameters with fine dressing times (nf) of 3, none-feeding dressing times (no) of 3, fine dressing depth (af) of 0.01 mm, rough dressing times (nr) of 3, rough dressing depth (ar) of 0.03 mm and dressing feed rate (Sd) of 1.0 m/min have been determined, that allow getting the best roundness tolerance.